Side-by-side / two files audio player for OSX?

What Pat said. If you have a MIDI controller I expect you could map notes to track soloing to make it smoother (especially if you have more than two tracks).

My own custom set-up uses a Launchpad so I can can jump to different patterns in a solo’ed track. I’m using a MIDI-to-OSC proxy to manage this. I’m also using about 40 excerpts from various reference tracks, not whole songs, but same basic behavior.

There’s also the Toggle Reference Track tool: https://forum.renoise.com/t/new-tool-toggle-reference-track/39281