An interdisciplinary journey towards an aesthetics of sonification experience

The aesthetic dimension has been proposed as a potential expansion of sonification design, creating listening pieces that reach the goal of effective data communication. However, current views of aesthetics still aim at optimising mapping criteria to convey the ‘right meaning’, maintaining a mostly functional view on what is considered a successful sonification. This paper proposes an interdisciplinary approach to the aesthetics of sonification experience, grounded on theoretical foundations from phenomenology of interaction, post-phenomenology, cross-cultural studies, acoustic ecology and deep listening. From this journey, we present the following design insights: (1) the design of sonifications becomes a design for experience, (2) co-designed during the interaction with each participant; (3) the sonification artefact gains a mediating role that guides the participant’s intentions in the sonification space; (4) the aesthetics of a sonification experience generates a multistable phenomenon, offering new opportunities to experience multiple perspectives over data; (5) the interaction between human participants and the sonic emanations compose a dialogic space. A call for action to reframe the sonification field into novel design spaces is now open, with aesthetics gaining a transformational role in sonification design and interaction.


Introduction
With the broad definition of communicating information through sound, the field of sonification has been the subject of research and development for more than thirty years [64], focused on how to extract and understand data relationships from acoustic signals.To achieve this, sonification usually encompasses an interdisciplinary approach, working with human perception, sound design, composition and interaction.
1 CISUC, Department of Informatics Engineering, University of Coimbra, Pólo II -Pinhal de Marrocos, 3030-290 Coimbra, Portugal Despite this richness of approaches, the field has been at a stalemate with regards to solidity and global recognition: John Neuhoff (one of the field's founders) has identified these challenges [34], listing the reasons as a combination of the subjective nature of sound [33] with (1) perceptive and listening differences between individuals, (2) the precision of vision compared with audition, (3) musical backgrounds of the sonification designers and users, (4) and the interdisciplinary nature of the topic.The multitude of dimensions to be worked upon establishes the ongoing difficulties of the field to reach the necessary credibility as a wider research interest.
One of the research paths to explore alternative approaches for sonification is to consider the aesthetic dimension.Aesthetics has been considered important regarding the perception and experience of a sound piece, exploring embodied interactions and mental processes in search for the 'pure meaning' of data.This expression translates the standing view within the field of a successful dataset communication through a correct mapping and interpretation criterion, leading the listener to understand with precision the sonified data and its inner relationships and patterns.Following a straight communication flow of 'information source reaches its human receiver through an information display' [64], the sonification field has been dominated by a functional perspective of data translation through sound.We argue that this unequivocal relation between data and its interpretation can be a reductive vision on how to design a sonification, linked to Neuhoff's list of issues [34] that still haunts the field.
An aesthetic turn in sonification [2] could maintain a design focus for usefulness and enjoyment, while also encompassing the subjective relation between sound and its listener.With recent studies developed through the lens of the subject perspective [47,62], the listener-sound subjectivity is welcomed for communication within sonifications.Besides the encoding process of coupling sound and data through a coherent mapping metaphor, this perspective considers the importance of the listener as the sonification perceiver and the centre of experience, developing an aesthetic relationship with the artefact through interaction (decoding process).
Such a shift on how to conceptualise this sonification process might stir needed transitions within the field and open space for new questions.Following this proposition, how can the transition towards multiple meanings be integrated as part of designing for the listener's interpretive process?What could we consider as sonification aesthetics, or even an aesthetic philosophy for sonification [3]?And, most importantly: how can we reform our understanding of the sonification experience to enable an aesthetic approach to its design?
Our purpose with this study is to understand what could be the foundations for an aesthetics approach to the sonification experience.By framing a sonification as an 'experience', we want to grasp alternative design approaches and perspectives that embrace the subjectivity of perception as a multi-meaning / multistable phenomenon.We argue that this exploration space does not hinder the communication purpose of data sonification, but in fact expands it, recognising and generating a space of varied listening outcomes and interaction dynamics.
Such an aesthetics approach to sonification must integrate and go beyond sound research, embedding knowledge from a multitude of research fields.We thus present a theoretical journey undertaken to gather this interdisciplinary perspective, from interaction design, phenomenological perspectives, models of aesthetics experience, cross-cultural studies, acoustic ecology to listening awareness.With an aesthetics of the sonification experience emerging as a generative research space, we seek to answer the two grounding questions regarding such phenomenon: (1) What is the aesthetics of sonification experience?(2) How does it manifest as a new design approach to sonification?
The remainder of this paper is structured as follows.Sections 2 and 3 provide an overview on current sonification practices, respectively current interaction framings and research on aesthetics.Section 4 enters the interdisciplinary narrative, gathering theories from Interaction Design and Aesthetics, Phenomenology of Interaction and Post-Phenomenology.Section 5 discusses the influence of culture in behavioral patterns and perception awareness.Section 6 circles back to present theories on sound phenomena, including Acoustic Ecology and Deep Listening practices.Section 7 discusses the generative potential of aesthetics for designing sonification experiences.The paper then concludes with a set of design insights, with a call for action to sonification designers to embrace a new perspective over aesthetics in novel design and interaction spaces.

Sonification and HCI
When we come to the field of HCI, sound still has a tendentious secondary role [23,51].A sub-discipline that has emerged is Sonic Interaction Design (SID), which aims to explore sound to "convey information, meaning, aesthetic and emotional qualities in interactive contexts" [51, p. 87].SID explores the design space beyond the use of sound as mostly a signalling function of a system, and elevates it as a central medium for communication and meaning-making.As described in a recent review by Johansen, van Berkel and Fritsch [23], SID is especially concerned with the role of the users and their relationship with interactive sound, incorporating theories of embodiment, multiple forms of tangibility and multimodality.
Within auditory displays, Hunt and Hermann have proposed the concept of Interactive Sonification, refocusing the design goal on how "humans interact with a system that transforms data into sound" [20, p. 274] through manipulating the data-to-sound transformations in real-time.This perspective takes the human to the centre of the process, focusing on how the system can be devised to creatively include the user's actions, while being adaptable to their needs and intentions.However, the authors distance themselves from the view that interactive sonifications can be seen as musical instruments: contrary to the expression purpose of musical instruments to translate gestures into sound, interactive sonifications aim at data analysis.A model description of an interactive sonification is based on a human-in-the-loop context, included in a responsive control loop where each human action influences or produces some kind of auditory result.
The research potential within interactive sonification lies in: (1) exploring a multiplicity of sonic views, embracing perspective changes over the dataset, (2) multimodal displays and their coupled influence, (3) how interaction can be balanced in a more flexible interface to embrace learning timeframes and (4) studying the ergonomics between actiondriven sonic responses and psychoacoustics.The end goal is how sound can become "as ubiquitous, informative and complex as it is in the real world" [20, p. 296] in interactive systems.
Interactive Sonification is already a subfield outside the usual listening-to-data approach.A recent example is the Photone [43] as a static mapping of data to sound that, when combined with an interactive exploration, can offer a varied and potentially rich space of listening.
Model-Based Sonification (MBS) is one of the formally defined sonification techniques, distinguished by employing a dynamic model that incorporates the user as a main driver.Defined as the "use of dynamic models which mathematically describe the evolution of a system in time" [19, p. 403], it follows an initial parameterisation and data-based configuration that offer interaction possibilities.Acoustic responses are triggered by exciting the system, mimicking everyday closed-loop systems, where interactions produce acoustic events that are perceived and interpreted by the human.MBS structures an interactive sonification scenario by proposing an interaction and sound generation model, therefore enabling interactive exploratory listening experiences.
Recent work by Seiça et al. [46] proposes Systemic Sonification, further advancing the conceptualization of sonification as a living system composed of sonic entities: the sound beings.It includes human participants and their interactive, action-perception explorations of a generative sound field, which enables a variety of purposeful dialogues, co-constructing a shared dynamic context.Designing with mutable sound beings, which reflect not only aspects of the data, but also the participant's intentions that evolve over time, pushes the boundaries beyond classic sonification, and into a systemic one.Enabling participants to actively reconfigure sound beings in the sonic interaction space, invites participatory dialogues in that context.While this may lead to variable listening outcomes, instead of considering this as a problem, we welcome this expansion to explore the generative potential of the systemic approach.
These approaches bring to the fore the important role of subject-driven exploration; they also open the door to multi-participant dialogues through interactions with the sonification space.We now move to the next section, presenting how aesthetics has been understood and discussed within the sonification field.

Aesthetics in auditory displays
"One hears repeatedly that we live in a 'visuallyoriented society' even though the ear tells the eye where to look."-Oliveros [37, p. 40] The term 'aesthetics' comes from the "Greek αισ θητ ικ ή aisthitiki, derived from aisthesis (i.e., perceived by the senses)" [13,4], initially regarded as the appreciation or perception of beauty.A concept that defined an aesthetic consciousness was the idea of a "special mental attitude" [25, p. 47], where the experiencer is separated from the object experienced.This demands a physical and mental distancing and a suspension of immediate judgments to fully appreciate its qualities.Kant pursued this view, where an aesthetic experience was only possible absent bodily desires [24].Alternative contemporary perspectives critiqued this notion of a particular psychological state.Artistic objects cannot be separated from the experience itself, with the aesthetic dimension being regarded as a clarifier and intensifier of qualities of "every normally complete experience" [11, p. 46].
"Sound is a naturally affective, aesthetic and cultural medium" [2, p. 177].Aesthetics in auditory communication and interaction has been a central theme of debate, and a definite influence to the user's appraisal and experience pleasantness.Embracing the sense-making role, aesthetics is brought to the field of sonification to design effective communication, which mimics the challenges of interactive systems to ensure a positive and compelling user experience [3].

Sonification and art/music
The relationship between science and art appears in the relationship between music and sonifications, which carries challenging conceptions: what are the boundaries between sonification and music, between a musically-structured sonification or a data-inspired musical piece?Can music even "have meaning beyond music itself" [3, p. 146], argued as one of the most abstract arts?Are sonification and music mutually exclusive, or could they share a common grounding [60]?
These two opposite perspectives are discussed by Vickers and Hogg [61], from which they proposed a circular scheme of 'Sonification Abstraite / Sonification Concrète', displaying multiple views on the sound object and its purpose.As a 2D space, scientific sonifications (ars informatica) and musical compositions (ars musica) are compared throughout the horizontal axis, with the vertical axis dealing with musique concrète and musique abstraite, contrasting direct data-tosound mappings to tonal and atonal music.As we approach the axes, the limits start to blur and the boundaries merge: on one side, we begin to have sonifications built with an artistic concern, and on the other music structured from some set of data or thought process, when the composer wants the listener to "understand extra-musical information" [2, p. 178].Barrass and Vickers [3] discussed the evolution of aesthetics regarding two major turns: the first as the beauty exaltation discussed in the previous section; the second, by embracing computational technologies in scientific fields such as data visualisation and data aesthetics, as a tool that embraces both function and information art.This is in line with a case study conducted by Leplâtre and McGregor [29] regarding the importance of auditory interface aesthetics, and whose results highlighted the interdependence of functional and aesthetic properties.
The second aesthetic turn is grounded on an interdisciplinary practice to balance the art-science dichotomy in novel techniques, thus embracing both sides of the spectrum.The second aesthetic turn is grounded As such, aesthetics must be regarded as a framework that works alongside the spectrum of sonic art and auditory display, whose barriers of separation must be taken down to fully embrace the interdisciplinarity between "music, design and science" [3, p. 166] that is inherent to the field.

Aesthetic strategies
Barrass, extending Udsen and Jørgensen's aesthetic turn [58] to the sonification field, also proposed an integration between art and science and an "holistic approach to functionality and aesthetics" [2, p. 178].This reflection resulted in the Listening to the Mind Listening (LML) concert at the Sydney Opera House.Considered "the world's first concert of sonifications" [4, p. 13], the call aimed at exploring if sonifications could be more than 'noise' and become a data-driven musical experience.The 10 resulting pieces used the same EEG dataset and had to follow three criteria of being data-driven, time-bound (timeline of sonification had to be mapped from the timeline of the data) and reproducible [4].Every submission sounded different, with styles that ranged from jazz, symphonic, soundscape, granular synthesis to electroacoustic and sound art.With 350 tickets sold out to the general public, its success showed that sonification can be a musical experience and evoke the "potential to develop a pragmatic aesthetic of sonification that integrates the appreciation of functional affordances" [2, p. 181].
The AeSon toolkit (Aesthetic Sonification) was a framework motivated by the role of aesthetics, combined with user-centred customisation and interface interaction.Beilharz and Ferguson [5] used concepts from information visualisation, information design and music to strengthen the aesthetic feature and increase the effectiveness of communication.This is also linked to the user's freedom while interacting with the system, allowing customised choices according to personal preferences, data characteristics and listening context that enhance "the general aesthetic quality and accessibility of data sonification and engagement with the information represented" [5, p. 1].
Grond and Hermann [16] listed a collection of auditory structures that can be applied as aesthetic strategies: (1) elicited sound as action feedback; (2) repeated sounds as pieces forming familiar and referential patterns; (3) conceptual sounds as data-inspired musical pieces; (4) technologically-mediated sounds, linked to the technology that renders them; (5) melodic sounds as mapping structures; (6) familiar sounds as routine sounds that sound familiar even when first heard; (7) multimodal sounds, linked to visual and other sensorial elements; (8) vocal sounds (mainly speech).
Filimowicz [12] proposed a two-dimensional space that explored two perspectives, with two personas, Fritz and Snow, which represent data-in-itself and listener-for-itself, respectively.The first, across the horizontal axis, expresses the tension between data in its purest form, untouched by humans, and the listener and his cognitive and perceptual abilities.Another two opposite forces constitute the vertical axis, as semiotic and compositional triads.The semiotic represents the sound to the interpreter, with rheme as its qualities, dicisign the sonified data form, and the argument the integration of the listener, the sound and the referent.The compositional represents formal data aspects, namely features and main structure of the sonification.A third diagonal force confront cognitive support against cognitive sabotage, where the first represents the data boundaries that build up associative representations, and the second a data-independent perspective over sound, reducing the data understanding concern to heighten the auditory emotional experience.The three parameters form an aesthetic conceptual space for sonification design, where the goal is to find the balance between the tensions.
Vogt, Goudarzi and Parncutt [63] conducted three experiments to evaluate aesthetic features in three sonifications, and their importance in sonification design beyond the tendency for functionality.Collaborating with musicologists, a test was designed to evaluate how the prior knowledge about a sonification mapping influences its aesthetic evaluation.The test was composed by two groups, with the experimental group acquiring prior knowledge, and the control group with no prior explanation.Although the results cannot be generalised due to the small number of participants, a few conclusions were outlined, namely the influence of musical knowledge, where musicians, in two out of three experiments, rated the aesthetic appealing higher than non-musicians.

Embodied cognition
Roddy and Furlong [42] explored the idea of embodied cognition, and how the human mind and cognitive processes are influenced by perceptual and bodily experiences.Embodied schemata appear as the basic unit of cognition, based on perceptual patterns of everyday life that we learn since birth, and from which we build conceptual meanings."Sound patterns become aesthetic experiences" [42, p. 73] through the cross-meaning of embodied schemata, which provides the context for understanding information.
Roddy [40] explored an embodied cognitive approach to designing sonifications, exploring embodied schemata as aesthetics.A model for Embodied Sonification Listening (ESLM) is proposed to define the process of meaningful listening of a sonification experience.The model is comprised by two sonic objects, where (1) the sonic dimension is an individual sonic characteristic that the user perceives as a single phenomenon, (2) the sonic complex is a group of sonic dimensions, and (3) the schematic knowledge is the listener's background-"physical, social and cultural environments" [40, p. 33] that influence perception.By applying meaning-carrying perceptual patterns of everyday life as sonic dimensions, the author explored vocal gestures, natural soundscapes and temporo-spatial motions to explore the embodied nature of auditory cognition.
Roddy and Bridges [41] theorised the potential role of embodied metaphors and aesthetics to adapt sonification processes to a general audience and discover a universal shared context" [41, p. 64].They proposed that, as body features create natural connections for interpretation, embodied cognition should be explored as a design process for sonification.As such, both the encoding and decoding stages are important, applying the same focus to the mapping and the user's embodied perception and communication processes.

Subject-position
Barrass and Vickers [3] highlighted the importance of user experience and the need to create sonification designs not as experience, but for experience.This open-ended goal demands novel design perspectives on how to create sensemaking paths, which unfold during user exploration.
A more recent reflection about aesthetics also embraces the subject perspective: Vickers, Hogg and Worrall [62] defend the user's role and embodied cognition as a subjectposition, with aesthetics becoming an essential vehicle in sonification design and through which auditory information is rendered and presented.Sonifications are a part of the user's acoustic environment, becoming "part of the user's embodied experience of that environment" [62, p. 89] and engaging with them through culturally and aesthetically organised senses.Music is inevitably one form of organisation; however, beyond a musical experience, sonification should be seen as an "experiential, ecological or perceptionaction aesthetic" [62, p. 106], which the user listens to in search of information.As such, the aesthetic dimension is indispensable for the meaning-making process, and cannot be separated from the informational / functional side.Listening encapsulates both dimensions, involving "the intuitive, the learned and the aesthetic, with emotion, mood, social circumstance and identity" [62, p. 103] of the user.Considering both the data and the user's contexts, an embodied experience can be created, with the role of aesthetics constructing the 'subject-position'.As "a way of guiding the listener" [62, p. 103], aesthetics can promote both the object of perception and also (and maybe more importantly) its perceiver.An ecological metaphor is thus composed, cultivating the user's innate and embodied associations to perceive the data, while establishing Roddy and Bridges' [41] encoding/decoding phases.

Limitations and expansions
With the subject perspective [62], the listener-sound subjectivity becomes a welcoming feature of sound communication within sonifications.Aesthetics guides the listening process as a "perception-action aesthetics" [62, p. 106] that promotes active listening in search of meaning.Meaning can be seen as multifaceted: by grasping acoustic communication as "all of the phenomena involving sound from a human perspective" [56, p. XI] that connects "listeners and communities to their environments through sound" [57, p. 194], we move away from the sound designer as the expert and we embrace the listeners in the process.An aesthetic dilemma [57] emerges in how we can join auditory practices with different listening scenarios and interpretative forms, embedded within cultural and individual contexts.
We can, in the end, "escape the strictures of taxonomy" [62, p. 106] for designing a sonification experience.However, despite the authors mentioning the idea of an "ecosystemic network of experiences, memories, imaginings and expectations" [62, p. 105] that integrates the users and their subjective backgrounds, the experience is still mostly constrained by the designer's intent, of what they choose to sonify and communicate from the dataset.In the end, isn't this intention similar to the 'pure meaning' utopia of functionalism?If the participant is to be taken as the central element of the experience, with their expectations, memories, cognitive foundations and emotional patterns, can there even be a single meaning?
A shift is needed to embrace a multi-meaning design that encompasses sound subjectivity as an open field of exploration of the sonification artefact.So far, we moved past sonification as a listening instrument, for it to become a whole instrument to be listened to, played and transformed.We now arrive at our main goal, where we dive deeply into the aesthetics of the sonic interaction phenomenon to better understand its essence and perception processes.

Journey through the phenomenon of aesthetics
This section presents an overall gathering of knowledge regarding aesthetics, bridging knowledge from a diversity of fields.We travelled across fields within HCI, philosophy of interaction, post-phenomenology, cross-cultural studies, acoustic ecology and deep listening to gather views on how an aesthetics can be understood and explored.

Aesthetics of interaction
In his work on aesthetics of interaction, Svanaes [55] starts by retrieving the formal definition of interaction: as a "mutual or reciprocal action or influence", we can dive into what encompasses something as interactive, the meaning(s) it gains, and the influence it contains as a social feature.To purposefully combine every element within the interaction, dynamic states, sensorial dimensions, its communication effect and how the experience evolves across time, is the focus of the Interaction Design discipline, centred on the relationship between the user and the object and "the action that define them in use" [18, p. 74].
Aesthetics appears as a key theme in this relationship, studied in Human-Computer Interaction from the beginning of the '00 s, with the term aesthetic of interaction that explores how human-computer interactions can produce "high-level experience" [27, p. 631].Aesthetics was characterised as a "guiding system" [27, pp. 628] that leads the design process and the user in their interaction towards a goal, performing a series of actions from which meaning is retrieved.
Udsen and Jørgensen [58] called the aesthetic turn to the cultural experience with the emerging digital interactions, in in which aesthetics arises as a new exploration tool for human-computer communication.The relationship between the aesthetic object and the aesthetic experience of the user can be explored through the following approaches: (1) the cultural, with the user as a part of an integrated system; (2) the functionalist, which enhances usability; (3) the experience-based, which addresses richer and more expressive forms of interaction; (4) and the techno-futurist, which concerns issues of perception, embodiment and the overall relation with how we live and think with digital technologies.
Another notion, proposed by Lenz, Hassenzahl and Diefenbach [28] is the idea of an aesthetic fit, which happens when the aesthetic is properly designed for a particular context, and from which beauty naturally emerges.The fit of aesthetic interaction is then a balanced relation between its attributes and each particular experience, when the motor-level How (physical parameters and usability metrics) expresses the be-level Why (emotional parameters of meaning-making and user's state of mind).It becomes a key aspect of research to understand these two realities, and the true nature of each experience to invite people to the creation and sense-making processes [39].
In the HCI field, Petersen et al. [39] proposed the concept of Pragmatist Aesthetics, which sees aesthetics not as an existing feature of nature, but as a potential that appears in our relations with everyday surroundings and experiences.Opposed to analytical aesthetics, where mind and body are two separate entities that work individually, pragmatist aesthetics focuses on their interdependency: it "encompasses the immediate sensational auditory, visual and tactile qualities of artefacts and the intellectual process of appropriating the artefact" [39, p. 271].Like Hassenzahl and Diefenbach [28], Petersen et al. [39] also refer to a tight connection with the context in which the interaction with technological systems takes place, and the user's personal past experiences and sensations, which can influence the use of the system in that particular context.
The aesthetic perspective comes to emphasise the "experiential aspects of interactive systems" [39, p. 274] and the user's freedom and exploratory attitude, encouraging play and discovery on how to experience the system.The user becomes an active, engaged agent combining both bodily and mental skills to enhance perception, encouraging an unique appropriation process of technology that creates "involvement, experience, surprise and serendipity" [39, p. 274].

Interaction gestalts
Another concept for aesthetics in interaction design was devised by Lim et al. [30], who presented an interaction gestalt as a set of composition qualities that the user experiences and evokes an emotional, meaningful reaction.The goal is to define principles of a design language for designers to shape their compositional parameters and produce engaging experiences.This language concerns the design target (the gestalt itself), its attributes and how to shape it, and the user who will experience the gestalt.
An example given as an interactive artefact regards a push button, which seems static when displayed on the screen, with its visual appearance not translating its full properties [54]; only when activated does it display a change, revealing its behaviour in response to the user's actions.A push button or a toggle, on screen, seem similar; it is only through interaction that their distinctiveness transpires.As such, when we think about the more basic units of an interactive experience, it is not just an element or action/reaction pairs, but complete behaviours [54].An interaction gestalt is then shaped by an internal series of attributes that define the inter-face, as material, style, metaphors, actions supported and forms of interaction, encompassing all "analogue input, full colour, hidden states, delays, animations, sound, algorithms and communication" [55].

Somaesthetics
The discipline of somaesthetics arose from the foundations of pragmatist aesthetics and philosophy [52].Active engagement with an artefact encompasses the central role of the body as a medium for all perceptive senses.The soma-"living, sentient, purposive body" [52]-is the focus of the somaesthetics.It is an approach within Interaction Design that explores the somatic subject as an active and ever-evolving medium for perception, and how the experience with the artefacts can enhance self-awareness, focus and mastery of the body.The interaction gestalt model [30] also integrates these sensory and affective dimensions in the experience with technology.The somaesthetics model recognises the importance of the somatic dimension in the user experience, heightening the user's and the designer's consciousness within the interaction loop that make interaction gestalts more effective.The somatic consciousness can then be deepened to empower our way of being and acting, with novel forms of somatic practice through interactive artefacts.
Perceived through a positivist or constructivist lens, we can look at the interaction process as something that is (1) technically deterministic, (2) dependent on the user with expected outcomes, (3) or an interactive, emergent reality that is constructed during experience itself.It is thus an important step to look at interaction as a complex phenomenon that allows multiple philosophical paradigms in its conception.

Aesthetic experience
"Every experience enacted and undergone modifies the one who acts and undergoes, while this modification affects, whether we wish it or not, the quality of subsequent experiences."-Dewey in [44, p. 113] Experience arises as an important concept to highlight the interaction continuum of a user with an artefact.According to Dewey [11], we may even distinguish an experience from experience, where the first has a beginning and an ending as a unitary or bounded moment in time, whereas experience has a continuous nature.Roth and Jornet go even further by stating that experience is not lived by individuals nor is owned by them; experience "denotes transactions in and across space and time" [44, p. 106].These transactions encompass and transform both the subject and the environment, both important actors in the experience.As such, experience through a cognitive or mental lens is sorely reduced; physical-practical, intellectual and affective dimensions within an experience are all factors of influence to the ones who live it.The authors specifically proposed an experience theory as an "irreducible whole" [44, p. 112], characterising it through two essential features: the open-endedness driven from its transactional nature, and the affective dimension that transcends the individual.It is from these elements that experience is formed and gains its transformational nature as well, modifying every individual and every subsequent experience [11].
Examples of this theory occur in educational scenarios (e.g. the classroom) [44], where teachers cannot exactly anticipate the flow of a class, the plenitude of conversational exchanges within it, how the students will react and respond at each iteration and what they will all become in the end.Independent of the intentions of its actors, they will be transformed through the experience.

Information processing model
In the last quarter century, various proposals of cognitive models were made to understand the stages of the aesthetic appreciation of art.Leder et al. [26] conceived an information-processing model to understand what psychologically attracts us to an art piece, what makes us understand it and ultimately improve knowledge and mastery of art.The authors consider how the exposure to art demands a process to "classify, understand and cognitively master the artwork" [26, p. 493] that constitutes the aesthetic experience, with the gradual positive affective states resulting in the aesthetic emotions.
An aesthetic experience is here understood as a "perceptual problem-solving process" [26, p. 499], constituted of loops of meaning-making until a satisfactory understanding is reached, as well as an aesthetic outcome.Resulting satisfaction and pleasure come from a successful processing and a sense of meaningful productivity.Although the goal is to gradually reduce ambiguity, the authors argue a non-need for complete resolution within art experiences, as it is "an artinherent feature that a residual ambiguity might be left open and accepted by the perceiver" [26, p. 501].

Aesthetic information processing
Marković's model [31] regards the aesthetic experience as a special experience distinct from daily, mundane events-"a special kind of subject-object relationship in which a particular object strongly engages the subject's mind" [31, p. 1].They define the aesthetic experience with three crucial aspects: (1) motivational through a fascination with the aesthetic object, (2) cognitive from the acknowledgement of its symbolic reality, (3) and affective, through a sense of unity with the object derived from both the aesthetic fascination and appraisal.It comprises a sequential narrative to understand the object and its expressive functions, and the compositional features that influence this.
Emotions as being 'aesthetic' are related to what emerges from an artistic appraisal, generated by the artwork (similar to the ones we feel in daily life), or by its structure and stylistic form.Aesthetic emotions here fulfil a large spectrum, from pleasure and surprise to anger and regret, as elements that provide "feelings of unity and exceptional relationships with the objects of aesthetic experience" [31, p. 11].Objects transcend to this level when they arise from the pragmatic to the aesthetic (symbolic) meaning: a natural landscape may provide ecstatic feelings of fascination and respect for nature, with the underlying emotions offering a full meaning to the aesthetic experience.

Cognitive flow model of aesthetic experience
Pelowski and Akiba's [38] cognitive flow model is centred on the individual and the concept of self-transformationcognitive discrepancy is needed to allow for a deeper reflection for true cognitive mastery and, ultimately, a renewed self.They argued that, as art "breaks in upon us" [38, p. 80], it becomes essential to understand the process of how artworks transform our acts of perception.
A pedagogical trend is also a hypothesis to increase cognitive mastery [38], providing contextual information and learning skills before experience to enhance feelings of mastery success; however, it may also substantially reduce experience enjoyment and even the role of the self in how the experience unfolds-control destroys discovery, and thus the possibility for self-involvement and transformation.
Both these authors and Leder et al.'s [26] conceptions focus, instead, on how the aesthetic experience has a disruptive dimension that transforms the act of perception itself and, therefore, the viewer.According to Dewey, conflict becomes an indispensable function of aesthetic experience [11], activating a self-reflection attitude that may lead to self-reorganisation and change.If the goal is just information or knowledge gain, the meaning of an artwork becomes unchangeable; it is just there to be assessed and processed as a "one-to-one match between artwork and perceptual schema" [38, p. 84], with no space for one's self to have a role in shaping information.
In a nutshell, this model comprises five sequential stages: (1) The user's pre-state of self-image, who holds a set of pre-expectations, tendentious behaviour and self-traits in response to the environment; (2) A process of cognitive mastery as a first assessment and attempt to classify, categorise and make sense of the artefact; (3) A secondary control to reclassify the artefact, when there is a discrepancy between what is expected and what is perceived (escaping can be an outcome if reclassification fails, ending the process); (4) A meta-cognitive reassessment as an active, conscious process for transforming one's self-image and involvement within experience, which invites them to "look outside" the problem [38, p. 89] and out of themselves; (5) And the aesthetic outcome of experience as the final stage, with a readjustment of the self and a "renewed/deepened cognitive mastery" [38, p. 89].
Aesthetic experience here is the whole transformative process through disruption, self-reflection, acceptance and expansion.Cage's 4'33 piece [8] is an example that offers a whole moment of silence and freedom, which opens a space for the audience to "become creative in the face of nothing" [38, p. 90].
Although the model is characterised as a 'cognitive flow', we found it to be curiously deviant from the cognitive trend, with the notion of how aesthetic experiences are spread across routine life.As a disruptor of the act of perception, and with an ultimate goal to transform perception itself, aesthetic experiences can lead to more flexible self-images, where we progressively become more open and permeable to external provocations if we acquire a consciousness of active and mutable perception [36]."Inexact essences" [22, p. 22] are simultaneously found during this process, where the term 'inexact' does not mean a discredit, but a relaxation of the need for exact definitions, welcoming ambiguity as part of the process of discovery [14] (detailed in Sect.4.5.3).

Flowering of experience
Think about the flowering of plants: the loveliness of a blossoming, although pleasurable to observe, can only be fully understood through its causal conditions.Soil, air, light, water resources, are all factors that make the flowering experience what it can fully be, "of which things esthetically admirable arise" [11, p. 12].Every living creature lives in an environment in constant interaction with its surroundings, connecting its bodily and sensorial frame to them, and adapting its life path accordingly.These biological connections reach the core of what Dewey considers the aesthetic within experience.Life as an overcoming of conflict and disruptions that brings significance, life as adaptation through expansion from which a balanced harmony arises [11].Equilibrium comes from a play between tension and release, as in music.Beyond a flow of change, it is about how every shift influences each other through active movements-order is reached by balancing a variety of transitional transformations.
Dewey's framing of art as an experience [11] defocuses from the expressive object and the materiality of the work of art.It regards the work of the artist as embracing past and future within the present [11], reflecting on past experience to provide an emotional and meaningful trace in the present, but also the urge and mystery of future endeavours, and even future actions that the present might unleash (e.g. the next stroke while painting).Expression encompasses both the past and the future in unison within and with the present, with the aesthetic experience emerging from the act of creation.To act is to devise a present link between what one is doing, what one did and what will do.
Meaning comes from both the object and its creation process.As such, it cannot be an unconscious act of 'intuition' that 'comes naturally'.Dewey [11] uses the example of a painter, who has to consciously understand the effect of every brush stroke and its influence in the whole artwork.An experience then becomes aesthetic from this iterative fulfilment and understanding, through the past-present-future reflexive acts.The body is also regarded here as the physical entity through which our living experience unfolds, and the intentional movements that arise from the body within experience [54].An experience is distinguished as aesthetic through the rhythmic series of exchanges, resistance and tensions, certainties and doubts, to an united shape of sequential arcs towards a fulfilling close [11].This sequence order, form, elements and flow are unique to each individual within an experience-"to perceive, a beholder must create his own experience" [11, p. 54].

Philosophy of interaction
As we have presented so far, the tendency within the HCI field has been to deal with the user's role through a cognitive paradigm, where the user becomes an information processor and a receiver of the artefact's outcome.This has been more apparent during the second wave of HCI theories [6], where interaction settings were community-focused within particular contexts.This generation embraced more proactive methods of prototyping and participatory approaches, which intended to resignify technology for appropriate contexts, needs and groups of use, both in the professional and personal spheres.However, even with the user as an active actor when designing technology, their levels of control were limited, constrained not only on how to use technology, but on how it should be used.The classic communication model of sonifications also follows this subject-object paradigm, which reinforces the view of the human as a mere receiver of information through triggering actions.
There was a paradigmatic change, coming with the third generation of HCI theory [6], where the context of technology use was expanded, mixed within multiple human activities, roles and places.From the private to the public spaces, workplace to leisure, home and everyday tasks, "the third wave HCI focuses on the cultural level" [6, p. 2].It embraces aesthetics, a transition between the cognitive and the emotional, and an overall focus on the experience technology offers and how it impacts the existence of each user.Interaction Design is much more than interactions: it is about the whole experience of the self and selves towards new forms of being and becoming.

Phenomenology of interaction
Encompassing phenomenological perspectives in the field was first approached by Winograd and Flores [55], who state the limitation of cognitive science in regarding symbols as one-to-one forms of being.One object means one perceptive capacity of use, with its existence in our daily life as being ready-to-hand; only when there is a breakdown in regular usage, either for failed expectations in its use or conscious reflection, does the object emerge from the background to gain new intentions of use, becoming present-at-hand.This distinction of the object over its background is called a transcendental reduction, in Husserl's theory, which attempts not to reduce the object, but to emphasise its contextual background, and the conditions that make a phenomenon appear to us the way it does [54].This is curiously connected to one of the Gestalt principles applied to sound design [53], the figureground distinction: it represents the idea that, for example, if you have a voice that pops out of a crowd, the voice becomes a figure against the ground of background ambience.The difference is that the Gestalt design intends to define different hierarchies of information importance (where one's attention goes to), while the phenomenological focus assumes the implicit background features that form the appearance of the phenomenon itself.
Phenomenological perspectives of Husserl, Heidegger and Merleau-Ponty came as a break to the cultural Cartesian dualism and the sole existence of two domains, the mental and the physical, distinctive and functioning separately.The cognitive view, with the body as just an "object for the mind" [54, p. 7], follows this trend of emphasising the mind and mental processes as the single, core decision-makers.In alternative views that encompass other dimensions (the body, for example), an object gains multiple forms and features with its use; interaction brings the object's potential for being.Anchored on the user's intention and context of use [55], one single action may encompass different intentions.Context also encompasses the cultural and personal background of the user, their lifeworld or phenomenal field, which "serves as a frame of reference and context for every experience of that person" [55].
The user's relationship with technology is surrounded by a physical space, highlighting the importance of their physicality and bodily presence (as part of their lifeworld) in how this relationship is developed [54].This brings us to the phenomenology of perception theorised by Merleay-Ponty, grounded by the core idea that every discipline, regarding humans and their relationship with the world, must embrace the fact that the human is part of that world.This being-in-theworld, embedded within a social, cultural and physical space, "is prior to both object perception and self-reflection" [55].We exist in the world as a bodily presence, both as a physical and material entity, and also as it is self-experienced-named the lived body.
Merleau-Ponty sees perception as an active movement towards stimuli, which occurs from how we interpret these stimuli through our lived body.It stands as an opposite view from the cognitive approach, with the human as a mere information processor that passively deals with information.There is, thus, no perception without action-"perception requires action" [55].
Iterative loops of action-perception are what constitute our active existence, with the body becoming the means by which we represent our intentionality towards the world.Turning an object around in our hands represents the intention of looking at it from different angles, to understand the object through coordinated movement between the hands, arms and eyes, visual and tactile senses.The lived body encompasses all senses, and it is a whole, undivided unity through which we perceive the world-it becomes, thus, an embodied intentionality [54,55].
Embodied intentionality may also go beyond the body itself, as it has the ability to extend itself through external tools.Merleau-Ponty's example of a blind man's stick represents how the stick becomes an extension of the body that allows the blind person to perceive what is around them-it becomes a part of their body schema [54,55].This bodily extension through artefacts may also happen with technology; in an RPG game, for example, where the player has an associated character, the actions of the character (e.g.holding a sword) become an extension of the player through the input controls, also enhanced by the emotional engagement with the character.
Our bodily space is mutable to our surroundings, influenced by our phenomenal field that shapes the directness of our actions and our self-awareness of body schema, and also every extension and instrument-mediated interaction that we experience; their dynamic nature, particularly, may lead to breakdown situations and abstract actions that invite us to unknown paths of exploration.These factors, when intertwined, are what allow meaning to emerge through interaction [54].
Following Merleau-Ponty's perspective, interaction is to be seen as perception itself [54].To press a push button to see resulting changes is an embodied perceptual act using the hand and the eyes, with a directedness of the hand movement towards the object.The feel dimension is what the user perceives of the resulting button's behaviour.This is termed embodied perception, as the interactions acted out through a perceptual and bodily movement that carries an intention for perception.These actions over the interaction gestalts are what Svanaes defines as kinaesthetic thinking, moving beyond a cognitive and logical reasoning to an emotional dimension that arises, as in somaesthetics, with bodily connected experiences.Sequences of both abstract and concrete movements (respectively distinguished as conscious or naturally-driven) can be combined and even surpassed; this freedom of the lived body to consciously experience appears as kinaesthetic creativity.A participatory design workshop example [54], where the participants were invited to become creators of new body-related functionalities by acting out future scenarios, shows how kinaesthetic creativity can be applied to the design process-"the best way to design for the lived body is to design with the lived body" [54, p. 27].
Designing interactive artefacts embraces interaction as an emergent process that allows the user to 'feel' the artefact and consequently perceive its properties and behavior.This demands detailed designs of the interaction gestalts, in particular how they embrace bodily experiences that consider the lived body as a whole, perceptual entity that guides the user's actions.It becomes, to this end, increasingly important to maintain a tight relation between the lived body and technology.This ensures a perceptual coupling in practice, designing consistent systems that support an effective communication of action-perception loops between the user's action and the system's responses.

Designing for multi-meaning
Wright, Wallace and McCarthy [66] proposed a reflection on aesthetic experience, with the aim of understanding the relationship between people and technology.They followed the research strand of Pragmatist Aesthetics [39], regarding as 'aesthetic' both the relation between the artefact and the user within a social, daily context, and also Dewey's orientation towards a fulfilled, connected life.Moving beyond the framing of aesthetic experience as limited to a theatre or an art gallery, they regard the experience as 'aesthetic' from what emerges from action, and from what is felt by the experiencer as a unity and fulfilling wholeness [66].
The aesthetic experience becomes the centre of interaction design, growing from just analysing the relation between humans and technology, but also changing the design process of digital artefacts from "the realm of functional 'gadget' into the realm of object with personal significance and uniqueness" [66, p. 19].Wright, Wallace and McCarthy do not propose an alternative methodology to user-centred design, but a new framing for designers to embrace concepts such as user, iterative design and user involvement.This new design lens brings the focus to how the user makes sense of the artefact, how the interaction journey takes place emotionally, sensually and intellectually, how it is embraced into one's life, and how the aesthetics of everyday experience is brought to the design process.The user's perspective becomes equally or even more important than the designer's intention, with emphasis on the emergent meaning in use.
Welcoming multiple interpretations and meanings within a single artefact can be regarded not as a flawed design, but a space for exploration [50].User-centred approaches shift away from problem solving and system designs that lead the user to the designer's intention, to iterative redesigns that reach meaningful user interpretations.What has been proposed is an heterogeneous solution where both are combined, creating malleable software that can "incorporate and balance multiple, perhaps conflicting interpretations and processes of interpretation in design and evaluation" [50, p. 101].Designing for multiple interpretations, or multi-meaning designs, require a few proposed design strategies [50]: (1) specify usability, leaving open interpretations of use; (2) support a space for interpretation that welcomes new, alternative interpretations by (3) hindering the most expected; (4) promote re-assessments by diminishing the imperative role of the system, (5) provide consistent interpretations, and 6. offer iterative opportunities for meaning-making that gradually unfold during the experience.

Ambiguity in design
We can also bridge the welcoming uncertainty of experience with ambiguity, usually regarded as a problem within HCI development, but proposed by Gaver, Beaver and Benford [14] as a resource for design.Characterised as "intriguing, mysterious, delightful" [14, p. 233], it embodies the perspective of the designer, while opening space for individual interpretations.As a property of the relationship that arises between each user and the artefact during interaction, ambiguity exists in context as well, demanding each participant to actively enter in the meaning-making process.The authors distinguish three types of ambiguity: of information and how it is presented to the user; of context, with meaning changing depending on the context of presentation, and of relationship, with how the user relates with the artefact.
A few tactics on how to explore different types of ambiguity are also listed [14]: (1) work with imprecise representations to explore uncertainty, (2) show inconsistencies or over-interpretations to raise speculations and spaces for interpretation, (3) raise doubts to encourage reassessment, (4) combine incompatible contexts or incongruous elements to shatter preconceptions (or at least try to), (5) break expected functions to provoke discussion, (6) propose unusual roles to welcome imaginative scenarios, and (7) offer elements with no explanation or disturbing relations to encourage discussion and reflection.
All these actions provide new perspectives for the designers to explore alternative interactive scenarios.By "crafting interactive designs that are engaging and thought-provoking" [14, p. 240], novel spaces for reflection and questioning can emerge, which might even question current social and ethical trends.

Meaningful interactions
Mekler and Hornbaek proposed a framework regarding the complexity of meaningful interactions [32], as a conceptual tool to understand meaning in interaction, and a practical formulation to design meaningful user experiences in the HCI field.Based on a literature review over meaning perspectives, the authors suggested five central elements: (1) connectedness between self and artefact, (2) interaction purpose towards an end-goal, (3) coherence in the sense-making process, (4) resonance as the immediate and unreflected sensation of positive interaction, (5) and significance as the importance and value of an experience.
This framework is presented intending to promote the meaning of experience when designing interactive artefactsthe interaction goal becomes the 'meaning-making'.The five central ideas within meaning can be combined during the interactive experience, emerging and vanishing to offer a space for multiple interpretations.

Experimental phenomenology
"I and world are correlated, that without the world there is no I and without I there is no world"-Ihde [22, p. 40] Ihde embraces experimental phenomenology as a passage from abstract studies to practise, where core insights and learning foundations emerge from doing (in the phenomenological practise).As a science of experience, phenomenology demands not an introspective attitude prone to subjectivism, but a reflexivity over the phenomenon.However, how do we get to the phenomenon-"that which shows itself in itselfthe manifest" [22, p. 15]?Phenomenology invites an opening to phenomena, with an epoché attitude that demands a suspension of preconceptions and expectations that can limit perception possibilities.The hermeneutic circle, or dialectic of interpretation within Ihde's framing, entails this paradox of embracing a whole phenomenon with an intent to enclose it within a definition of its essence and way of manifesting (what and how).
The first level of a phenomenological research comprises: (1) face a phenomenon as it appears, (2) describe it, do not explain it, as explanations carry intentions and meaning, and (3) horizontalize all of its appearances, allowing for all appearances to show themselves as equally important.
The second level brings the study of all possible variations within particular instances of a phenomenon, characterising their structural invariants and boundaries that form the 123 essence of the phenomenon.In the end, intentionality is what shapes the experience, and a transcendental part of its invariant structure by defining boundaries, direction and the totality of possible events.

Intentionality
Intentionality is the relationship between what is experienced and the mode of being experienced.The subject-object analysis might occur at a later stage, when the experience (as past) is described.But, if "to perceive is to perceive the world" [59, p. 122], separating the human and the artefact cannot occur within living experience.Experience requires the relation between the experiencer and what is experienced, as we must always experience something."The experiencer and the experienced are inextricably bound up with each other" [59, p. 122] through an intentionality for acting.
In this context, Ihde proposes a technological intentionality, which translates the mediating role of artefacts in human existence (more in Sects.4.6.4 and 4.6.5),where our directness of movement is driven by an intention for action.It is inevitably relational, with a directional and referential mode towards what is experienced, and the phenomenon always referring to the point of view and experiencing mode of the experiencer-the 'I', bearer of experience."I know myself only in correlation with and through the world to which I am intentionally related" [22, p. 40].

Multistability
When an "item appears, [it] appears only as situated within and against a background" [22, p. 37].Retaking the transcendental reduction of an object over its background [54] (presented in Sect.4.5.1),Ihde portrays a phenomenon with three main elements: (1) the core object, centre to our attention, (2) a surrounding field that stands in the background as a contextual framing, and (3) the horizon or fringe, which limits the borders of perception.
At every moment in time, there is always a face of the phenomenon that is hidden and visually absent from one's point of view.This absence-in-presence is the latent potential emerging from every other perspective that is not the individual's current one; changing it leads to phenomena variations.We have then an inner horizon of all the perspectives within a phenomenon, and the external one that delimits the phenomenon itself-what it is now, in all its views, and what could become.Both horizons are in constant co-presence within a phenomenon, and they are what elevates an object to a transcendent state through "a play of presence and absencein-presence in our perception of things" [22, p. 41].This play only exists within experience, just as artefacts only gain their mediating role and meanings in the context of use [59].This contextual mutability is regarded as the multistability of arte-Fig.1 The Necker Cube, taken from [59], as a visual example of multistability facts, with the Necker cube (Fig. 1) as an example of several perspectives within just one representation [22,59].
The play of consciousness of what we perceive, how we are perceived, and what we might be simultaneously not perceiving constitutes the "genuine transcendence of the world" [22, p. 42].According to Ihde [22], these hidden potentials are the genesis of knowledge expansion, and it is only when one is aware of their absence-in-presence that one might seek them.Intentionality is then what drives this expansion, triggered by the self-awareness of our limited perspective through reflexive moves on what is and, ultimately, could be-this is the phenomenological constitution of meaning, as the self-conscious reflexivity that invites reality variations.

Imaginative variations
A phenomenological deconstruction of the multistable phenomenon opens the universe of variations, not only over a contextual background and its ordinary stance in it, but over all possible interpretative views raised during experience, supported by multistability itself.
The phenomenological shift embraces a phenomenological attitude towards the world, questioning the established familiarity with an object to see it in alternative ways.These alternatives will probably feel strange, uncanny or even uncomfortable at first, but a necessary emotional journey to reach new perceptions.This is very much in line with Gaver's welcoming ambiguity [14], designing artefacts that embrace moderate degrees of uncertainty, incongruence or seemingly incompatible relations.Pre-expectations and beliefs are mandatorily suspended, or at least toned down, for new viewpoints and meaning-making paths to emerge.Cage's 4'33 piece (referred in Sect.4.4.3) is an example of playing with uncertainty.We may regard it as a multistable piece, not focused on the musical moment as commonly framed, but a performance of silence and the "incidental sounds which occur and now become the 'music' " [21, p. 189].
Embracing multistability is an opener in itself, as the iterative expectation may generate variations within the phenomenon.Variations become, in a way, multistable themselves (transient understandings); following an epoché attitude facing multistability, our perspective gains a growing dynamism and potential for expansion when the phenomenon's variations become mutable within experience-"for every group of phenomena being interrogated, ascendance to the open context is irreversible" [22, p. 74].By questioning "the very structures of possibility" [21, p. 200], we reach the ultimate phenomenological thinking: a nearinfinity of the experience's multistability.
All sounds are instruments in the making, and their variations opportunities for improvisation.A curious example of multistability in practice is given by Ihde [22], regarding a room filled with musical instruments.With some instruments known and others unrecognisable, everyone was invited to enter and participate with a single instruction: play.It started with a general discomfort; soon after, participants began experimenting, even with familiar instruments, alternative ways to make sound (e.g.hammer on piano strings).This session illustrates a scenario where the play phenomenon emerged in context as a multistable event of play forms.Musical instruments gained their role and meaning as instrumental tools through play, surpassing the designer's intent with varied use trajectories.Improvisation, as an unpredictable form of deliberate play, embraces imaginative variations essential to phenomenological practice, with each one carrying new subsequent directions to explore [22].This example translates the action-perception loops that portray our embodied intentionality [54,55] to play music, and bodily actions to explore the sound space of the instrument.It also represents the instrument-mediated experience in which the instrument becomes an extension of the body, creating an extended body schema between the human and the world, through the instrument.

Post-phenomenology
A subsequent framing of phenomenology as an experimental practice emerges-postphenomenology-that sees technological artefacts as mediators of human relations with the world, while also providing new framings for relating with technology itself [22,59].Technology, as a spectrum of complex, multi-dynamic interaction and processes, is elevated as a bridging element of mediation, a lens of perception with which we act within our reality.Mediation "coshapes subjectivity and objectivity" [59, p. 130] as a transformative element of perception, reinforcing aspects of reality and reducing others.The mediation role of artefacts may influence behaviours by inviting or inhibiting forms of involvement, and human perception by amplifying or reducing interpretative views.For example, the organisation of a dinner table can pro-mote an egalitarian or hierarchical form, revealing underlying intentions or differences in cultural roots.
Verbeek mentions Merleau-Ponty's phenomenology of perception as a methodology for action, how we relate with each exchange through a contextual lens-things are not just the things themselves, but also how we perceive them through our relations.Reality is not 'what is', but what is disclosed to human beings, "the world-for-humans that arises when they act and experience it" [59,108].This multi-reality view has its origin within human intentionality towards a phenomenon, surpassing a consciousness for knowledge as a subject-object dichotomy, to a consciousness for acting and being-in-the-world in a multi-relation context.

Multistability of technology
The postphenomenology perspective comes from the contextual realities that emerge from technology-mediated relations.Different tools for writing (typewriter, pen or word processor) influence writing styles and even the outcome, as they provide distinct compositional speeds and correcting functions that might change the way we think on what to write and how it gains form [59].
An artefact, beyond being cherished and esteemed, gains its importance and attachment with the relation we form during its use.Attachment is what truly binds us to an object, with a concrete materiality beyond the conveyed meanings, related lifestyle or even contextual importance.For an artefact to last across time and space and enact "true cultural durability" [59, p. 225], the author states two major needs: (1) maintenance of transparency, as an understandable and accessible functioning that ensures return to a ready-to-hand state when they break to the present-at-hand; (2) user involvement in their functioning, encompassing user participation as an element that impacts either their functionality or integration in daily lives.These properties demand an artefact design that is human-dependent, where we become involved in not just what artefacts do, but how they do it.A musical instrument only gains its role, exists as a function and grows as a meaning-making tool by being played-and it is through this kind of slow-growing attachment that durable human-artefact relations develop.
A turn to practice is needed to devise aesthetics as a co-shaper of artefacts, establishing relations with the world through their use and experience.If artefacts play a mediation role between human and reality by shaping their perception, aesthetics becomes an important aspect to consider in that mediation as well.All sensory relations developed during artefact experience form its aesthetic dimension.This perspective of aesthetics encompasses the experiential aspects that emerge during practical interaction [39], how they can be designed as a combination of interaction gestalts [30,54,55], and how users explore their lived body and the 123 somatic consciousness [52] as a perception channel for action.Post-phenomenology is an encompassing perspective for interaction designers to consider, reflect and use to create technological extensions that play with how humans explore and develop embodied relations with the surrounding world.
5 Culture and contexting "(...) the future depends on man's being able to transcend the limits of individual cultures"-Hall [17, p. 2] One of the most discussed limitations within the sonification field is how to deal with the individual differences and contextual background of each listener.The culture dynamics in which the individual is immersed influence their individuality, regarding listening and sound-related habits, but also social behaviors and how their habits are formed and fed.
Culture is socially constructed and apprehended within shared contexts [17], whose differences are often noticed by one individual when faced with a culture different than their own.Culture awareness arises in this confrontation, which usually leads to a sense of strangeness, higher selfconsciousness and unpredictability of actions.
Behavior exchanges-to what one pays attention to-is largely a matter of context, with contexting what allows handling its inherent complexity.For the contexting process, one can use internal guidances based on innate processes, previous experiences, or external cues deriving from the current situation.To guide the function of contexting, we can work on a communication continuum, with high-context (HC) communication on one side, where contextual information is primarily hidden or assumed, or with low-context (LC) communication, where contextual information is explicitly carried in the message [17].
We can regard this spectrum on how to work with more or less explicit forms of communication.We can also consider what comes implicitly and 'naturally' as what demands a high degree of stability and cultural integration (HC), and what needs a decoding and learning process as what demands change and transcendence of one's cultural bubble (LC).To balance this spectrum is to balance a pattern-seeking attitude within life.And to achieve this, the concept of action chains is discussed by Hall to illustrate the transactions between all living beings and the environment [17].
Action chains define our sequential and tendential behaviours in life, and are intimately related to our cultural habits or standards.According to Hall [17], five categories influence perception and form our behavioral patterns: (1) the subject or activity, (2) the situation at stake, (3) the status within the social system, (4) past experience, (5) and the embedded culture.These tendencies are a part of a cultural unconscious-if we become aware of it, in ourselves and others, we become more permeable to external modes of existence and action.And even with the social tendency to achieve homogenization within and even across cultures, it is by embracing cross-cultural contact that strength and resilience is built.Man, although impossible to separate from the environment in which they function, is "above all a learning organism" [17,173].
This supports the argument that a universal design in our creations is an overall utopian goal, which further points to the potential of designing for multistability.Accepting multistable phenomena is to accept the cross-cultural differences and the multidimensional lens of each participant.

Listening phenomenon
"Look at a tomato."[35, p. 74]-the contemporary philosopher Alva Noë begins a chapter, entitled "Experience of the World in Time", with this seemingly casual provocation to invoke the idea of objects as being timeless, existing as a whole entity in the present, with hidden elements or parts.They surpass our experience as a continuous unity, even if we can only see a portion-the absence-in-presence [59].However, we sense them as a whole, with a consciousness of all possible variations of the phenomenon [22]-in this case, all sides of the tomato.

Temporality of sound phenomena
A sustained note from a soprano is described as a sound phenomenon that occurs within the now: holding "the perceptible quality of temporal extent" [35, p. 76], it encapsulates the past, the present and the future.Objects are timeless; events, on the other hand, are "creatures of time" [35, p. 77], temporally extended.This relationship with time becomes crucial when dwelling within the sound medium-it is not by chance that the example given by the author regards the act of singing.There is an intricate relationship of sound with time and space, as sound temporality gives a corporeal form to what is heard-a shape, a material, a spatiality [21].
The author argues precisely the existence of a sound continuum as a 'trajectory', sounds that we first listen rising from the past, culminating in the present, and extending towards the future.An arc of sound translates a continuity that embraces meaning across time, a temporal structure that carries our relation to what is now coupled with what was and what will be.There is, thus, a temporal sequentiality of sounding through the listening act."I do not hear one instant followed by another; I hear an enduring gestalt within which the modulations of the melody, the speech, the noises present themselves" [21, p. 89]-this is auditory intentionality.
An example as simple as pronouncing a word goes beyond acoustic properties such as pitch, timbre, loudness (from the object) to an arc of meaning, with an intentionality towards the event-"events are sequences with a sense" [35, p. 78].The arc of sound embraces this sequence of meaning as intentional arcs, within Merleau-Ponty's framing [35]: a sustained note from a soprano carries the singer herself, her voice, her vocal choices, actions and, therefore, intention.Past and future are implicated as a continuum of sense-making across time, with crescendos and diminuendos of sense-making that unfold while the eventful experience exists.The figure of an arc is also, curiously, a metaphor to the temporal fluctuations within a sound envelope, with an emergent attack, a sustained establishment, and a decay to silence until final release.
Retaking the three-element portrayal of a phenomenon of object, field and horizon [22,59], we have a sound presence, precise, definite and an attention focus as our core object, the auditory field as a situated sonic context that surrounds us an in which we are immersed, and the auditory horizon understood as a temporal boundary.The sounds that 'suddenly appear' have a temporal edge "into the equal nowhere or nothingness of the no longer present" [21, p. 102]-the pastpresent-future continuum of sense-making [35].The dance between sound and silence in our auditory horizon sows an expectation of what comes next: in a music piece, for example, we tend to hear additional tones or the upcoming ones [21].This anticipated motion is what intertwines timeframes for auditory sense-making, with the auditory horizon as an infinite spatial limit, from which sounds emerge and unveil the sense of time itself [21].
Noë argues the influence of familiarity when we hear a sound: when it is unfamiliar, strange, unbeknownst to us, we tend to discard it-sound perception may be, up to a certain point, limited to what we understand.The continuous listening to a sound gradually diminishes an initial opacity and discomfort, and we begin to experience it more fully, with a gradually constructed meaning that feeds the motivation to keep listening.As we listen repeatedly to a music piece and it becomes familiar, we become more able to appreciate its details and intrinsicalities.The intentional act of listening can be regarded as phenomenological, in the sense that its pursuit for learning the phenomena also allows "to more and more clearly show themselves" [21, p. 85].
Objects always exist; it is the event of their experience that makes them available to our perception, and our sensitivity to those events what allows our perception to unfoldexperiences are "temporally extended patterns of skillful engagement" [35, p. 80-81], whose events we live as they play out in time.Cognitive mastery occurs during experience itself [38], with every learned skill offered gradually, depending on the how the arc of sounds unfolds through variable arcs of interaction [22], in multistable journeys [22,59] that offer multi-meaning emergence [14,50].

Auditory imagination
"Insofar as anything can be given a voice, it can become an instrument."-Ihde[21, p. 192] Ihde evocatively states that "existentially things 'speak"' [21].The auditory experience can be framed as an intentional listening of all sounds, named by Ihde as the voices of the World.Those voices, besides echoing the self's voice, gather "voices of things, of others, of the gods" [21, p. 147], while also echoing the listener's own voice.This layered listening also embraces the imaginative mode as a second modality of experience.
The imaginative mode is discussed by Ihde as inner speech [21], an inner form of language that regards the multi-facets of the phenomenon through the lens of what a phenomenon might be.Auditory imagination is one main argument the author uses to distinguish auditory from visual phenomena.The auditory field has infinite boundaries that surpass the frontness of the visual; as such, auditory imagination in what lies ahead is also continuous.As "meaning in sound embodies language" [21, p. 150], our inner speech regarding the auditory word is in constant dialogue with our other inner perceptions and the voices of the world.This process fluidity gives the perception of auditory experience a dynamism unlike its visual counterpart, with less disruptions and breaks, but more detours and alternative paths in our perceptive processes.
Listening to the listening itself is regarded as polyphonic listening, in a parallel duet between what is perceived and what is imagined [21].The sequentiality and reflexivity of the listening act, through the imaginative-perceptual co-presence, elevates the auditory experience to a heightened awareness of what is and is not sounding, ultimately composing the multistability of auditory phenomena.The phenomenology of the auditory experience gives voice to the invisible; listening to those voices enables a reflective and learning action to listen to what is hidden beyond the surface, and to uncover "the language of the unsaid" [21].

Acoustic ecology and sound awareness
"(...) we are all composers of the universal soundscape which we can become attuned to if we learn to listen to it as if it were music"-Truax [57, p. 193] The perspective of a communication ecology of sounds comes from the foundations of Acoustic Ecology, the "study of sounds in relationship to life and society" [45, p. 205], where a soundscape is seen as a whole system of interrelated parts [56] existing in equilibrium.
Natural soundscapes and the sound of life as close to nature brings an inherent acoustic quality that gives each sonic happening a sense of importance, a relevant event with "strong symbolic character" [45, p. 169] that comes to consciousness and appeals for attention.As C.G. Jung explained, an element is symbolic "when it implies something more than its obvious and immediate meaning, [carrying a] wider 'unconscious' aspect that is never precisely defined or fully explained" [45, p. 169].The never-reaching fullness of meaning implies the quasi-infinite multistability of phenomena [22,59], in this case multiple listening perspectives, with an inherent ambiguity [14,50] that goes beyond a single function-related meaning.
The listener as the one who listens is also enhanced here to a multi-perspective: the soundscape of the world, when regarded as a musical composition that is continuously crafting itself, embrace us "simultaneously [as] its audience, its performers and its composers" [45, p. 205]-we are soundmakers [56].Acoustic communication then deals with the systemic relationship [56] between sound, its listener and the environment through sound, which is regarded as a communicational approach to sound.It gathers the interrelated parts of a dynamic system, reforming the linearity and cause-effect exchange to a "mediating relationship of listener to environment through sound" [56, p. 11].Sound gains a mediating role in human existence, with sonic artefacts embracing a technological intentionality through our actions in context, and thus following a post-phenomenological view that coshapes reality and our being-in-the-world [22,54,55,59].

Elements of a sound
In auditory experience, "sounds are 'first' experienced as sounds of things" [21, p. 60], where its flow is composed by a mix of individual rhythms and harmonies.The sound object, as "the smallest self-contained particle of a soundscape (...)" [45, p. 274] is distinguished from sound events, where the objects gain their contextual perspective within a particular space/time moment, becoming symbolic when stirring "emotions or thoughts beyond its mechanical sensations or signalling function" [45, p. 169].Meaning then emerges from both the structures patterns of sound itself (the sound object) and also from the listener's contextual background and surroundings [56,57]-together constituting the sound event.
Schafer [45] classified four sound perspectives: (1) physical or acoustic features, (2) the way these are perceived as psychoacoustics, (3) the function or meaning they carry in semiotic or semantic terms, and finally (4) their emotional or affective qualities (regarded as aesthetics), standing as the most difficult classification due to the variety of ways it can affect each individual.
Retrieving the Gestalt theory applied to sound [53] (mentioned in Sect.4.5.1), the figure-ground layering was first described by Schafer [45], who brought the idea of a figure as the signal or soundmark, the ground as the ambience layer that surrounds it, and the third field element as the soundscape itself, from where observation takes place.Schafer also highlights the phenomenological constructions of the field in how one perceives the figure-ground elements in their contextual space.
This triangular relationship is similar to Ihde's framing of a phenomenon [21,22], with a central object, the contextual field and the horizon as the perception boundaries.These formations of sound phenomena follow the temporal nature of sound; as, "above all, sounds exist in time, and (...) they create and influence our sense of time" [56, p. 65], with the past-present-future flow forming the intentional sound arcs [35] and changing the way we interact with it.

Acoustic design
A balancing exchange between the variety of coexisting sounds and their complexity is crucial: too few variances may lead to monotony and meaninglessness, whereas too much information can become overwhelming and unordered, both leading to an unaware attitude.When this equilibrium is reached, coherence is maintained from perceived regularities, punctually stirred with subtle variations that together encompass a satisfying sound listening experience [56]-as the regular ocean waves or melody variations around a tonal centre.
Acoustic Design aims at retrieving an aural contextual culture [45], with each individual as a 'participant-designercomposer' in the overall soundscape.This multi-role goes beyond the control of the single-sided perspective of the designer as the creator [50,56] to embrace every individual as part of the creative process.Man, as a pattern-seeking creature in all things, seeks to understand patterns and logic within sounds as well, with the auditory system tuned to detect variations and compare known to novel patterns [56].The role of the acoustic designer is then to understand the range of ways sounds can be combined to create unique orchestrations.
Soundscape composition is regarded as a continuum of practices [57], from sonification and realistic world-to-sound representations to the conception of sonic imaginary worlds, evocative of inner memories, metaphors and symbolisms.Beyond music theory-related changes (in tempo, pitch, loudness and others), Schafer [45] lists four principles for the acoustic designer to work upon: (1) a respect for the ear and voice to be heard, (2) awareness of sound symbolism beyond function, (3) of the natural rhythms and tempo of soundscapes, (4) and all its balancing mechanisms of growth and grounding (yin and yang).
Sound balance must, ultimately, seek how to embrace silence.Sound only exists because there is silence, a blank state from which any sound source gains life."Man fears the absence of sound as he fears the absence of life" [45, p. 256].This fear, coupled with the incessant rhythm and loudness of modern urban life, has detached the human being from moments of peaceful contemplation and mental recovery.Silence also offers a keenness of listening, with every sound gaining a brilliance and importance in its emergence through a listening awareness-"if we could extend our consciousness outward to the universe and to eternity, we could [even] hear silence" [45, p. 262].

The depths of listening
"Can you imagine listening beyond the edge of your own imagination?"-Ione[37, p. 24] Listening is a sensorial ability that grounds us to our surroundings-if we listen, we are aware.To listen is to embrace what Pauline Oliveros [36] named as the space/time continuum of sound, characterising our soundscape as the sonic context that surrounds us.The practice of Deep Listening was cultivated by Oliveros as a way to expand our perception of sounds, beyond what is immediate and ordinary.It welcomes an awareness of the present moment, an impartial listening to the whole space/time continuum of sound that (1) sharpens our attention, (2) entices our memory, imagination and sensorial receptors, and (3) expands our consciousness of sound and underlying relationships between every sonic element.
As a process training, Deep Listening demands a gradual practice that involves the self and the body (with sequential body work and breath exercises), consciously perceiving the listening action, the listening focus and the listening body as an active presence belonging to the surrounding soundscape.Exemplary exercises include the 'Field Recording' to listen and record different types of soundscapes, the 'Extreme Slow Walk' to move as slow as possible to notice all body movements, or the 'Listening Journal' to daily write down one sonic experience [36].Schafer [45] goes even further by proposing the embodiment of a tourist role, wandering a soundscape as a visitor to notice variations in known places.These examples are all ways to experience a different reality by offering new perspectives over phenomena [22]-in this case, by listening.
Awareness of the present moment expands the self's notion of being a sound-producer, a soundmaker within the soundscape.This expanding attention applies both focal attention, directed to an object of attention for gathering detail through exclusive listening, and global attention, embracing the space/time continuum of sound as a whole entity through an impartial and open inclusive listening [36].This complementary relationship presented by Oliveros is similar to Ihde's [22] panorama of a phenomenon within the auditory field's spatiality: the global regarding the "surround-ability of sound" [21], and the focused directionality towards a sound detail.

Multidimensional listening
A symbiotic relationship between every sonic element takes centre stage, listening to understand their presence and their being-in-the-[sonic]-world.The concept of multidimensional listening [36] represents how all human dimensions interact in the act of listening.By engaging in multiple sensorial ways, we may, consciously and unconsciously, grasp parallel flows of sound, understanding their temporal and spatial dimensions embedded within a context.A simple conversation is an example of this multidimensionality [36], gathering how we can be aware of one's voice, our perceived meaning, the other listening cues, memories that surface, the follow-up dialogue we imagine, the physical space where we stand, the surrounding soundscape, among others.From our surrounding sounds to auditory imagination [21], all form the "interplay of sounds in the whole space/time continuum" [36, p. 12], extending one's receptivity, 'observation' skills, intuition, compassion and understanding from the openness to listen.Animals and babies provide examples as natural deep listeners [36], which listen fully to others' presence, completely attentive for survival, intake of environment cues."Listening comes before speaking" [21, p. 116], and it is through listening that we gradually learn to communicate and interact.
Oliveros also refers to the importance of silence as "the space between sounds" [36, p. 14], from where all sounds arise as their origin.The silence of the context can be welcomed not as a void or the end of life [45], but a "near silence of what can be said" [21, p. 162], a field of possibilities and a space of potential sonic births.
The consciousness of the listening act embodies the arc of meaning [35], the sense-making that embraces the temporal continuum within a sound.The conscious act of openly listening may serve as a creativity opener: a particular piece from Oliveros, 'Open Field', invites one to consider as an 'art experience' every sight, sound, movement or place that comes to attention during daily routine.The multidimensional awareness allows an expansion of perception, altering one's view of reality, former knowledge and action repertoire as a reshaping of the self [38].Deep Listening invites us to the edges of perception, and to move beyond those edges, allowing for aesthetic experiences of renewal and transcendence of the self [38].It is a mediating act between humans and the surrounding world [59], of intentional listening-acting towards that world [54,55], where kinaesthetic creativity emerges through connecting the embodied self, the world and consciousness itself.

Quantum listening
"As you listen, the particles of sound decide to be heard" (Ione, in [37, p. 9]).This is the idea of Quantum Listening, a quite adventurous concept from Oliveros, published posthumously.By consciously becoming aware of the listening act-we listen to ourselves listening-we enter the ever-ending 'listening effect', simultaneously creating what we listen to, while transforming ourselves in the process [37].It expands the boundaries of an aesthetic experience as well, with the listener embarking in self-transformation, while becoming a co-creator of the aesthetic phenomenon.
Sound is understood as reactive particles in a potential force field [37].Co-transformation takes places by interacting with this sound field, where each listener affects the field by listening to it, and vice-versa-thus the quantum effect.Sound becomes a sensorial portal to new realities formed within the act of listening.

Reclaiming listening
The most fundamental ability that an acoustic designer can deepen is, in conclusion, to listen [56].Deep Listening designers, as Oliveros named them, may thus have a fundamental role in transforming the narrowing and disconnection caused by urban living [36] and, as "listening shapes culture" [37, p. 30], transforming our surroundings that impact our social presence.
Retrieving the phenomenological roots [21] (presented in Sect.4.6), more than a reduction to vision (the first reduction that elevates one sense over the other), we have the second reduction of vision itself, which ultimately diminishes sense to give primacy to significance [21].The focus of sound or vision on just 'information', while proclaimed by current technology, lessens the entirety of the phenomena by narrowing variations.We can introduce, through this statement, the need for sonification itself to arise from the functionality tradition and embrace the interdisciplinary voices to conceive multistable designs.
Listening to the self demands acceptance of all past history, future anticipations and potentials that join together within the present.We argue this openness to the self also leads to openness to others, a porous existence that invites mutable perception boundaries and, with it, aesthetic listening experiences.By awakening the natural potential of listening, a culture of listeners can arise and have a transformational role in shaping society-if we learn to truly listen, we may learn how to create new dialogues in community.

Aesthetics and the design of a sonification experience
The interdisciplinary journey and knowledge-seeking behaviour from multiple fields offers insights and alternative views over how we can regard sonification as a multistable phenomenon.Tracing back to our first research question, how can this relationship shape an aesthetics of sonification experience?

Generative aesthetics
We argue the multistability of the sonification phenomenon is an enabler of the aesthetics approach, which possesses a generative power that promotes a diversity of design explorations throughout the experience.Beyond generativity in the design space, generative interaction spaces can emerge, through interaction paths that provide freedom of action for its participant.With this non-linearity, designers also gain new opportunities, welcoming the exploration potential to create alternative experiences.By engaging participants in developing their universe of meanings, the design process becomes a universe of potential co-design approaches.These meanings emerge from curious exploration of possible interaction journeys, from the known to the unknown, from the routine to the unexpected.Aarseth's theory of ergodic literature [1] speaks to the exploration of alternative paths: the cybertext example, with its non-linearity, demands a multi-path reading process that translates an iterative movement of text selection.This reading is designated as ergodic, "derived from the Greek words ergon and hodos, meaning 'work' and 'path' " [1, p. 1].The multistability in sonification also embodies a generativity in its ergodic exploration, where the 'work' is the active listening attitude embraced to uncover meaning.
We may then say that we arrive at a formulation of sonification that embraces scientific research of generative potency [15].The generative capacity of a theory is described by Gergen as the capacity to "challenge the guiding assumptions of the culture, to raise fundamental questions regarding contemporary social life, (...) and thereby to furnish new alternatives for social action" [15].The sonification researcher is invited to leave the traditional positivist-empiricist paradigm of reaching a systematic theory of universal interpretation [3] and objective sound representation, in favor of a generative experience capable of generating multiple interpretations.
From a dispassionate observer, Gergen [15] invites the participant theorist to emerge.As a perceiver of variations on a phenomenon [22], a key role of the researcher is thus to embrace the multistability of studied phenomena into their research, their potential, how they influence each other and how they can be amplified.Sonification as a multistable phenomenon grows from just a solidified explanation of a one-sided phenomenon.With multiple "opportunities for meaningful dialogue" [3], the sonification space is designed for open exploration and interpretation of data, with the participant as an interpreter and co-creator.The designer does not thus design the final experience, but the experience space where its various facets may be unfolded-its multistable potential.

Multistable sonification
Embracing a phenomenology of sonification experience is to see it as a multistable phenomenon with multiple facets of exploration, parallel dimensions to be unfolded as the interaction progresses.In this sense, we argue that, by iteratively interacting with a sonification space, we may sequentially unfold one single facet of this time-based phenomenon, or dynamically unfold fragments of different facets.There is one single sonification phenomenon, with potential parallel layers co-existing, from which we may uncover and compose fragments of data during interaction as a meaning-making process.We may also regard its multistability dependent on distinct listening attitudes: one sonification space may be experienced differently depending on a combination of the design space conceived and the participant's choice.It is, still, the same phenomenon, but multistable and generative, whose participants gain not only a participant-actor role in the interaction field, but also a composer of their evolving sonification experience.This is, ultimately, the aesthetics of sonification-a perception expander through the multistable phenomenon.
As such, the designer must accept and embrace the unpredictability of each experience path, as much as the deterministic sound generating process, with an outcome that will be distinct for each participant with their lifeworld.The exact challenge lies in how to design an inevitably unfinished experience, to which the recent systemic proposal is a possible answer.

The systemic framing
Systemism as an enabler of aesthetic experiences was recently proposed by Seiça et al. [46].A systemic sonification is a dynamic sonification conceived as a living system [7,9], which responds and evolves depending on human interaction.An integrative space emerges from an organised community of sound beings, sonic entities of mutable structure and adaptable behavioural mechanisms.The sound being is the main sonic entity within the systemic sonification space, defined as an "auditory element whose behaviour evolves with external interactions, either from other sound beings or from human intervention" [48, p. 174].We may say it is a sound object that manifests within the interactive space and responds to contextual phenomena in a series of sound events.Each sound being results from a sonic manifestation of the system, and a manifestation of human perception in the interactive sonic field, whose exchanges compose sonic dialogues [49].These exchanges embody a phenomenological grounding of "perception requires action" [22,54], or of "action-perception loop[s] mediated by sound" [51, p. 107].Ultimately, as understood by Seiça et al. [46, p. 77], "perception is action", and it is through the iterative exchanges with the sound beings that meaning-making processes unfold.
The driving force of this proposal is to offer scenarios that can amplify the emergence of aesthetic experiences through interacting with the system, framed as "a subject-inclusive aesthetic meaning-making system" [48, p. 172].Seiça et al. embedded the transformative outcome as the purpose of the aesthetic experience [38], which expands the initial cognitive boundaries of the experiencer.The human participant, by interactively dialoguing with the sound beings, consequently "experience[s] a self-transforming process" [46, p. 80].Embodying the central role of the experiencer, they create their own interactive journey through an active listening attitude, and action-perception loops that feed the iterative sense-making activity.A proof-of-concept was recently published [48], using a touch interface with a continuous interaction flow, "embodied through the tips of our fingers" [48, p. 177] and coupled with active listening to grasp the meaning behind each action.

Systemic multistability
The systemic thinking provides a conceptual grounding to explore an expanded sonification design space, and alternative design approaches for interacting with sound.This brings a need to consider designerly-ways-of-knowing [10] in the sonification field, possibly resulting in new design processes and interactive systems.As it amplifies the boundaries of design thought, the systemic thinking potentiates descriptive and predictive abilities, for the designer to develop features of a systemic sonification scenario and speculate on its applications [65].
The systemic framing generates an ergodic space, proposing a multistable dialogue between participants and sound beings.Through the sound being concept, the systemic perspective embraces an instrumental mediation designed at its core, offering new spaces for conceptualising sound designwith new whats, we also gain new hows.The potential generativity of an aesthetics approach to sonifications can transform them into contextual, unique and mutable sound narratives that unfold for and with each participant context.

Implications for design
This interdisciplinary journey composed a theoretical grounding for an aesthetic approach to sonification experience.To understand how it manifests as a new design research approach (our second research question), we identified the following set of insights.
The composition of sonifications becomes a design of experience-A sonification, usually conceived as a linear, goal-driven composition, becomes an experience to be designed, embodying both the past (the listener-participant lifeworld and the designer), the present and a future of explorations that unfold during the action-perception arcs of interaction.
The sonification system plays a mediating role, influencing the participant's exploration of the sonic field-The sonification artefact carries the intentionality of its designer.As an instrumental mediation, it gains unique functions in the interaction context through its technological intentionality, either empowering or conditioning the participant's actions and carrying their intentions as well.
The sonification experience is co-designed during interaction-The sonification experience, more than assuming the designer perspective to define a path, is co-composed during experience itself, where the listener-participant becomes a co-designer of their interaction journey.
The aesthetics of a sonification experience generates a multistable phenomena-The role of the sonification designer is to create a system of composition possibilities, to be completed in the experiencing act.This space promotes multiple perspectives over the sonification phenomenon, embracing its multistable nature as a design opportunity for meaningful experiences.
A dialogic space is created by co-listening, co-acting and co-creating the sonification experience-The interaction between human participants and the system's sonic emanations composes a dialogic aesthetics within the sonification space.
By accepting multistability not as a design flaw or communication failure, but as a potential design approach, the multiple meanings emerging in interaction become a new goal for experiencing data.The communication goal of sonification becomes experiential, opening the field to new perspectives for design and research.

Conclusion
Thirty years have passed since the establishment of the International Community of Auditory Display (ICAD), with auditory displays officially regarded as a research field for sound communication.Despite ongoing efforts, inherent difficulties still hinder the field's credibility and widespread use, such as sound subjectivity, perceptive and listening differences between individuals in a visually-oriented society, musical influence and the interdisciplinary nature of the topic itself.
Aesthetics expands the design of sonification artefacts, providing a more compelling and intuitive data mapping that guides the listener in the experience, cultivating their embodied associations and presence.However, views on aesthetics within the field have been following the recurrent functionalist tendency, seeking to design and refine the sonification artefact towards the 'pure' or 'right' meaning of data as a successful end-goal.
With this paper, we presented a theoretical journey that seeks to gather knowledge from multiple research fields to propose an interdisciplinary construct, based on conceptual foundations of interaction design, phenomenology, postphenomenology, cross-cultural studies, acoustic ecology and deep listening.We deconstructed the design approach to sonification by proposing a multistable view over the sonification phenomenon, as an aesthetic approach that embraces multimeaning design.
Embracing a multi-perspective view demands a researcher that embraces not only their own perspectival view, but also accepts multistable phenomena as a design feature, goal and approach.The composition design of sonifications becomes a design of experience, co-designed during interaction with each participant.The sonification artefact plays a mediating role, gaining unique forms in the interaction context and guiding the participant intentions in the sonic field.Exchanges between human participants and the system's sonic emanations compose a dialogic space from which the aesthetics of sonification arise.The aesthetics of a sonification experience generates a multistable phenomenon, embracing the multiplicity of subjective perspectives over the sonification phenomenon and offering new opportunities to experience data.
We end this study with an open call for action to reframe the sonification field into novel design spaces.A sonification experience transcends the classic, systematic production of sonifications, with aesthetics gaining the transformational role of expanding the field of sonification design, interaction and research.
the Regional Operational Program Centro 2020.The first author is also funded by the FCT -Foundation for Science and Technology, under the grant SFRH/BD/138285/2018.

Funding Open access funding provided by FCT|FCCN (b-on).
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material.If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.To view a copy of this licence, visit http://creativecomm ons.org/licenses/by/4.0/.