Mapping Midi to the Spiral Array: Disambiguating Pitch Spellings

Abstract

The problem of assigning appropriate pitch spellings is one of the most fundamental problems in the analysis of digital music information. We present an algorithm for finding the optimal spelling based on the Spiral Array model, a geometric model embodying the relations in tonality. The algorithm does not require the key context to be determined. Instead, it uses a center of effect (c.e.), an interior point in the Spiral Array model, as a proxy for the key context. Plausible pitch spellings are measured against this c.e., and the optimal pitch is selected using the nearest neighbor criteria. Two examples are given from Beethoven’s Sonata Op. 109 to illustrate the algorithm. The algorithm is implemented and the results used in MuSA — a music visualization software using the Spiral Array. We present and analyze computational results from test runs on MIDI files of two movements from Beethoven’s Piano Sonatas Op.79 and Op. 109.

Partial funding provided by a Women In Science and Engineering grant and by the Integrated Media Systems Center, a National Science Foundation Engineering Research Center Cooperative Agreement No. EEC-9529152.