[LeifH12345]

I do not suggest messing with the speed/time of digital recordings. What I would recommend is use a multi-track audio mixer (I think audacity can do that?)

Keep one recording as one long file, and split the other as needed. The drift of two digital recordings is minimal, so an average song of say 3-5 minutes should stay in sync. Make the splits during applause, or at times where there's very quick + sharp samples (eg. drum stick count ins, snare cracks, claps if they're taped from the same location, etc).

If you can figure out which source is slightly shorter, keep that as the control (one long file). Then choose key moments to make transitions. Split and delete tiny snippets of the second source (thousandths of a second) to re-sync as needed. If they are nice clean waveforms, you can do this by eye once you get the hang of it, but always listen back every time you make an edit. If you're trying to sync a soundboard with an audience source, there can be phasing issues with bleed from stage monitors and such. Not much you can do about that besides find a good middle ground.

Then once you check everything and it sounds perfect, come up with the right mix, export the new wave file. That's how I do it. I can always hear it when someone messes with the speed and it bothers me to hear that. But to each their own. I also use the same method when syncing video and audio.