Really cool concept! I'm a fan of micro-heavy games and this felt like just the right amount of micro for me. Genius to have the powerups play together in the same scale. It was very effective. I beat the glitch boss but kept dying after.
Some things you may already be aware of, but wanted to share in case you're looking for improvement suggestions:
1. I walked out of the screen and my character was never able to come back
2. Cooldown on the solo is really hard to understand. I wasn't sure when I could and couldn't use it.
3. I really liked the idea of having 1-5 amplify certain types of attacks, but it took some getting used to for my brain to associate that Bass = AOE, Strings = Single target, etc. Might make it easier on the player to just call it their intended upgrade like AOE/ Single Target instead of musical terms.
4. It was hard to know when I got damaged and felt the death was very abrupt when it happened
Overall enjoyed the game and character designs a lot! Excited to see where it leads!