Wow! That's a great game!
I`m a huge fan of hollow knight, and could see the references, specially from the 'mosquito' things.
The rythm movement is very cool, but it's not quite clear. I get the idea that you should listen to the instruments to perform certain actions, but sometimes i feel that it's actually on the offbeat. Like, the double jump seems to work on the beat that the saxophone is NOT playing. Also i was never able to time the wall jump, i've used it just by pressing very quickly.
The main thing you should actually update asap is that messages from pickups disappear too quickly. Maybe add another key just to close them?
Nonetheless, great job! Hope to see it further developed!