How would one interpret audio files to facilitate synchronized playback?

Would you look at the bitrate, BPM, tuning? All of the above? I’ve been thinking of playing several songs at once since I was twelve. Frankly I’m surprised there doesn’t seem to be any musical framework in official versions of audio files. You could try to put both songs on the same BPM but you’d probably find the BPM isn’t adhered to well enough to prevent the songs from diverging. At this point I’d be tempted to dive into fourier analysis and never be heard from again.