How or what to play two tracks in one click?

Question

Audio

There are two tracks, almost identical: one is 3 minutes 11 seconds long, the other is 3 minutes 15 seconds. For a single listening, they seem to be the same, but since the duration is different, then there are differences in something. It can be in any absolutely moment of the tracks, so I want to find out in which one. The thought arose that it would be nice to play them together (in one click) with something, even in mono: even if one file goes to the left earphone, the other to the right! It will suit me! .. But with what? And How?..

Answer 1

Audacity?

Answer 2

It's not entirely clear why, but VLC can play files in parallel.
Not in one click, although you can write some kind of "batch file".
And "mixing" will not work (in the sense of making some road louder).