audio subtraction not working


it’s driving me insane, can you kindly tell me what I’m doing wrong?

I recorded two wav audio tracks using the overdub feature on my digital piano. I’d like now to subtract the two in order to isolate the new contribution and save this as a third track.

I can’t figure out how to do this. I tried all sort of configurations where I import the tracks and invert one of the two, however they keep playing, they don’t cancel themselves out thus revealing just the difference.

Here are the files, what am I doing wrong?

I’m on the most up to date Audacity on windows7 if that matters

Many thanks

ok the two files are not in sync with each other (but they should as they’re being overdubbed from the same source a kawai mp7se).

I need to figure out a procedural way (python) to offset files, any help would be most welcome thanks

I’d just as soon not agree to anybody’s analysis cookies.

Have you ever gotten this to work before?

I’m not exactly sure where to go with this. What do you expect the difference to be? the errors between the two performances? What’s the goal again?

to isolate the new contribution

Oh, I think I got it. You overdubbed and got one performance with the backing track and one with both backing track and the new performance mixed. Right?

You can’t split the second pass into two performances later. You are supposed to end up with the backing track and the new track separate after you overdub.

Make sure you are recording from a real thing and not a service or digital construction. If you like to record YouTube shows (for example) you may easily have this problem.

This is my machine.

Screen Shot 2018-10-12 at 16.14.57.png

Built-In Input is a real thing. It’s a socket on the back of my computer that I can reach out and touch. You may be recording from WASAPI, Stereo Mix or What-U-Hear. Those are fake things. They’re special software packages you use to record internet sound.

What are you recording from according to that panel, and what kind of microphone do you have?


Use Audacity’s time-shift tool to get them perfectly in-sync …

You’ll need to zoom-in until you can see individual sample points.