Separating Voices in Polyphonic Music: A Contig Mapping Approach

Voice separation is a critical component of music information retrieval, music analysis and automated transcription systems. We present a contig mapping approach to voice separation based on perceptual principles. The algorithm runs in O(n) time, uses only pitch height and event boundaries, and requires no user-defined parameters. The method segments a piece into contigs according to voice count, then reconnects fragments in adjacent contigs using a shortest distance strategy. The order of connection is by distance from maximal voice contigs, where the voice ordering is known. This contig-mapping algorithm has been implemented in VoSA, a Java-based voice separation analyzer software. The algorithm performed well when applied to J. S. Bach’s Twoand Three-Part Inventions and the forty-eight Fugues from the WellTempered Clavier. We report an overall average fragment consistency of 99.75%, correct fragment connection rate of 94.50% and average voice consistency of 88.98%, metrics which we propose to measure voice separation performance.