Pitch- and Chroma-Based Audio Features

Automatic music processing poses a number of challenging questions because of the complexity and diversity of music data. As discussed in Sect. 2.1, one generally has to account for various aspects such as the data format (e.g., score, MIDI, audio), the instrumentation (e.g., orchestra, piano, drums, voice), and many other parameters such as articulation, dynamics, or tempo. To make music data comparable and algorithmically accessible, the first step in all music processing tasks is to extract suitable features that capture relevant key aspects while suppressing irrelevant details or variations. Here, the notion of similarity is of crucial importance in the design of audio features. In some applications and particularly in the case in music retrieval, one may be interested in characterizing an audio recording irrespective of certain details concerning the interpretation or instrumentation. Conversely, other applications may be concerned with measuring just the niceties that relate to a musician’s individual articulation or emotional expressiveness.