How to make an Acapella/Instrumental-version part 1 – the phase-cancellation method


DJingIn this tutorial-series I’ll explain how to make acapellas or instrumental version of a song. Please keep in mind that none of them produces perfect results. Some are more useable than others. Today we start with the phase-cancellation method. You can use it if you already have either an Acapella or Instrumental-version of a song, which must exactly match the original song in terms of length, pitch, loudness etc. The more the two version vary, the worse the results are going to be.

If you don’t want to read this tutorial I also made a video showing the workflow:

The theory

The first question is: What is sound in general ? Therefore I’m using a definition of

Sound is the quickly varying pressure wave within a medium. We usually mean audible sound, which is the sensation (as detected by the ear) of very small rapid changes in the air pressure above and below a static value.

So sound is a wave oscillating at different frequencies. Imagine adding one wave to exactly the same wave. The amplitude will be twice as high, because they add up. At the same time adding one wave to the exact opposite wave will cancel the amplitude. The phase-cancellation method uses exactly this fact to get rid of parts that exist in both parts of the song. All you have to do is put both tracks above each other in two audio-tracks and invert the phase of one of the tracks. After that in the best case only the part you wanted to isolate will remain. The following picture illustrates this concept.

To put that into practice…

I’ll show you now how to use the phase-cancellation method in Ableton Live. You can use any audio-sequencer with the ability to invert the phase of a stereo-track.

  1. Put both tracks in different audio-tracks of Ableton and put them exactly above each other. Zoom in to the lowest level to get the best results.

  2. Go to ‘Audio Effects’ and drag an ‘Utility’-effect on one of the tracks. Now turn on the ‘Phz-L’ and ‘Phz-R’-buttons at the bottom of the ‘Utility’-effect to invert the phases of both channels of the corresponding track.

  3. Listen to the mix! If there is still a lot of the original track in it, zoom in to a low level and try matching both tracks again. You should stop the playback and hit play again after moving a track, because sometimes Ableton doesn’t instantly refresh the result. If you’re still not happy with the result you can add some EQs to manually improve it.You should also listen to the whole track as sometimes you have to match single parts of it again. If the result is bad you should check if both tracks do really match, maybe you have to correct key, pitch or volume.

The conclusion

That was pretty easy, right? The other methods require you to smirch your hands a bit more (some will make you wallow in dirt). However this method delivers the best results, but it comes at the price of requiring an exactly matching instrumental- or acapella-version of the song, which you don’t have in most cases. If you’re really desperate and just want to extract a few parts you may create instrumental loops and match them to the full version, but that can also be a pretty fruitless effort.

It’ll take me a while to write the follow-ups as there is a lot going on in my life. I’d really appreciate your comments, thought and maybe even tricks on this topic.

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