Separation of synchronous pitched notes by spectral filtering of harmonics

This paper discusses the separation of two or more simultaneously excited pitched notes from a mono sound file into separate tracks. In fact, this is an intermediate stage in the longer-term goal of separating out at least two interweaving melodies of different sound sources from a mono file. The approach is essentially to filter the set of harmonics of each note from the mixed spectrum in each time frame of audio. A major consideration has been the separation of overlapping harmonics, and three filter designs are proposed for splitting a spectral peak into its constituent partials given the rough frequency and amplitude estimates of each partial contained within. The overall quality of separation has been good for mixes of up to seven orchestral notes and has been confirmed by measured average signal-to-residual ratios of around 10-20 dB.