This game is super cool! I'd love to see more of this. As a musician myself I'm always looking for different ways music gets incorporated/focused in games.
I like all the different music bits getting layered as you progress. That's super cool. However, I think the actual "solo" mechanic was a bit buggy. I kept having issues with it not showing up when I wanted it to/disappearing. It was difficult to accurately hit those buttons while also running with WASD. I think the different modes are a cool concept but didn't see much difference I guess in the visuals to know that those attacks were doing something different from the "Balanced" mode. As a rhythm game I think having the standard shoot abilities being tied to BPM could be cool as well. But that's ultimately a design decision left up to y'all.
The art, SFX and music (of course) are all really solid so keep it up!
I think the ideas are there, I'd work on polishing your execution/UX. Keep working on it! Good job y'all!