Really interesting concept, i don't know much about music, so I'm pretty sure a lot many cool things were lost on me. But that being said, clearly a lot of effort was put into it. Art is nice! Gameplay wise i got a little confused. At the start i thought the combo/rhythm sequence was going to be a really "core" part of the experience, but i ended up not using/understanding it really.
If this were my game (which is not, so i probably have very different design objectives than yours), i would kind of design, some enemies to be, highly weak/resistant toward specific instruments, to push the player to adapt into different situations. Of course, this requires a lot of iteration, time, and design, cant really fit all that in a 2 weeks game jam. That being said, i don't have to much experience on this kind of game, so my feedback may not be the most adequate. Nevertheless, is a cool concept, with really cool music and sound design that is directly linked to the gameplay which makes it stand out. Congrats on making such a cool entry while adapting to the best of your team, keep it up!