Digital Music Editing

Given that I have an MP3 of some song, and an MP3 of that song’s instrumental version, is there a way to use this to my advantage to output an acapella track?

I seem to remember something from class once noting how one could take the original track, then take the instrumental, do something to it, mix the 2 tracks, and get “everything else” (in this case, the vocals) out of it.

Does anyone know more about this, or if it’s possible?

What you’re thinking of is phase cancelation. When you take one sound, copy it, flip it 180 degrees out of phase, and put it over the original sound it results in nothing.

In theory, this would work if the instrumental version of the music was the exact same music used in the lyric version… and given you could sync the two tracks perfectly together.

I’ve never tried this so I’m not sure what would happen to the vocal track. I don’t think you’d end up with a nice clean vocal track.

I’m in the middle of a recording session at the moment. I could actually try this for you and see what happens.

Well, I gave this a go. It seems the single problem is going to be the timing. I was unable to exactly sync up the two tracks. Even though the tracks were from the exact same section of the song, extracted the same way, there was enough slight variation in their starting points so they wouldn’t line up.

I suppose I could have gotten it had I spent more time fussing with it.

But in theory, yes, it should work.

Timing aside, this will not work with songs that have undergone lossy compression such as mp3. The vocal+instruments and instrumental mp3s will suffer different losses during compression. The different losses will be quite noticable when trying to subtract the instrumentals. You’ll get a lot of noise.

You know, I thought about the varied compression last night. I think it still would work with mp3 files, but it would be glitchy.

I was playing with wav files last night.

Wanna try for me? :smiley: