I liked the concept! Some thoughts from me:

1. The game was fairly fetch quest-y but I think even the fetch quest format could be interesting with more storytelling around the instruments/people involved.

2. The rhythm game part was fine and straightforward but would get repetitive fast. I have like a million hours on Crypt of the Necrodancer though, which has lots of novelty in it.

3. It could also be interesting to do something like Terry Rileys's "In C" (or perhaps more interactively "In Bb" https://www.inbflat.net/ ), have you considered it? Though I did like hearing some of the parts line up together too.