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I am looking to reverse engineer tracks by using "phase cancellation". Very often (especially in electronic music) a later part of the track may contain material from the beginning of the track plus some added elements. For instance a drum section, then with added synths and/or bass. By using phase cancellation it is then possible to extract only the synth and/or bass. This technique is also very common for extracting acapellas based on a song and its intrumental version as explained by this video.

The issue is that this technique is very sensitive to slight tempo changes or inconsistencies. Even after very careful slicing of a loop, inversion and alignment in Audacity it is quite likely that I end up with a portion of a 1 bar loop which is perfectly phase cancelled, and a portion which is slightly out of sync and in which the kick or other drums punch through. I can't seem to get a smooth workflow which would enable me to isolate and extract all the different parts of a song.

I think a couple of strategically placed and aligned warp markers on both tracks might do the trick by slightly stretching and compressing the track here and there to assure alignment of the opposing amplitudes. This would be similar to warping an image to making it align with an underlying map (for those who are familiar with GIS). However Audacity seems to be poorly equipped in the area of time stretching, and warp markers are something I've only seen in ableton live as of yet.

Does anyone know of a foolproof technique of doing this such that I can reverse engineer individual components of a track? I'm not looking for something fully automated, but anything which can allow a feasible workflow would be most welcome. I'm also open to programmatic solutions using python but I hope that won't be necessary....

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  • What are you planning to do with the tracks, not having copyright to them? Commented May 31, 2020 at 21:19
  • IF you have access to a 'minus vocals' version of the track, as the video shows reasonable results are possible. But how often is that going to happen?
    – Laurence
    Commented May 31, 2020 at 22:45
  • The point is not necessarily to make an acapella. The point is to reverse engineer the individual elements of the track such that I can remake it for educational purposes.
    – user32882
    Commented Jun 1, 2020 at 6:11
  • JamKazam sells recordings of tunes already broken out into the individual parts. You could consider that as well.
    – Duston
    Commented Jun 2, 2020 at 13:19
  • I would like to figure out how to do it myself....
    – user32882
    Commented Jun 2, 2020 at 13:29

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