I used Paul’s Extreme Stretch (PES) to take a hammer dulcimer + violin improvisation and divide it into seven streams based on just intonation relationships to A at 55 Hz. This harmonic filtering is a feature of PES – the parameters were 12 harmonics and and a bandwidth of 1 cent. The above graphic (click on it for a larger version) shows graphically the amplitude relationships and also on the far left the frequency in Hz for each track. At the very end you hear a very different sound – that is a few seconds of the original improvisation. PES has been updated and this is a better demonstration of the technique.
William Newbold made a video for this piece (with some editing of the audio)