Extending Alignment Algorithm for Polyphonic Comparison

Existing symbolic music comparison systems generally consider monophonic music or monophonic reduction of polyphonic music. Adaptation of alignment algorithms to the music leads to accurate systems, but extensions to polyphonic music arise new problems. Indeed, a chord may match several notes, or the difference between two similar motifs may be a few swapped notes. Moreover, it is difficult to set up the substitution scores between chords. In this paper, we propose a general framework for polyphonic music which permits to directly apply the substitution score scheme set for monophonic music, and which allows new operations by extending the operations proposed by Mongeau and Sankoff [1]. From a practical point of view, the limitations of the size of chords and the number of notes that can be merged lead to a complexity that remains quadratic.