Distortion after changing key

I used the change pitch effect and it caused the piano to become distorted (like a tremolo effect). I undid the change pitch effect, but the distortion remained. What can I do about this?

Time stretching will also cause a similar kind of distortion, but using the “Undo”, should return it to how it was before unless the data has somehow become corrupted.

You can sometimes minimise the distortion effect by repeating a small change several times rather than making a big change in one go. If you don’t mind changing the tempo at the same time as changing the pitch you can use “Change Speed” which does not cause this kind of distortion.