Sounds like an audio driver issue - when your audio driver runs at 48 kHz instead of 44.1 kHz (if it’s supposed to run at 44.1), everything gets pitched and speeded up. Funny stuff may happen when switching between sample rates - I run into these issues sometimes when swithching between working with Cantabile (which I run at 44.1) and Studio One (running at 48 kHz, because my recordings from my Mackie mixer are at 48 kHz). These days, I absolutely make sure that I’m not running both programs at a time, plus when starting any one of them, I take a quick look at my audio driver info dialog to make sure my sample rate is set correctly.
So I’d guess that you had run some DAW at 48 kHz before running Cantabile and somehow the sample rate got “stuck”. For a concert, I’d definitely check sample rates after starting Cantabile - and maybe check a test tone against your guitarist during sound check - and don’t turn off anything after sound check