Remove audio 1 from audio 1+2 audio file?

@SteveG_AudioMasters_  is right - mp3s unlikely to work . . .

Here's the method if you want to try via Mike Russell.

https://www.youtube.com/watch?v=vNvJKBg3yds

Sorry, no chance. For a start these are MP3 files, and as such you'd never achieve a sample-accurate lineup of the two files, because they would decode differently. And that's what you need if you are going to do a subtraction; identical material in both files, and it has to be sample-accurate if it's to work at all.