I like the enemies and character art! There's an unique artstyle in here that I enjoyed a lot, especially with the theming and everything. I did notice that the text looks small when fullscreening the game, so it'd be cool to have the text scale be proportional to the screen size.
The gameplay concept is super interesting. It's a mix of a roguelike with Parappa the Rapper. I think this game would play really well with a controller, since it felt a bit tough to walk around with WASD to avoid enemies, whilst also using 1-5 to do the tune combos. Maybe what you guys can do is have the player be able to also use Right Click to point where the character shuold automatically walk to, so that the player can focus on the 1-5 on the keyboard side of things.
I also thought it was super dope when I realized that getting the upgrades/instrument units wwas leading into a music slowly being formed with the addition of each instrument. It feels like an idea that has a huge amount of potential.
As a matter of fact, that can be said for this entire game. These concepts are super interesting and it feels to me like they hold a lot of potential. I really like it!