That was some pretty spunky music. I really like the overall setting of this game. There's a lot of charm in helping a skeleton ease up during his performance while you're dodging piano keys. I also like how you added in the green keys and the words of encouragement boxes, because they incentivize players to actually move around instead of standing in one spot.
The gameplay itself does get somewhat repetitive after a while since the keys move in the same direction. Maybe add some horizontal or diagonal moving bullets, but that wouldn't really make sense with the piano aesthetic. I would decrease the speed of the green keys though, because oftentimes I would chase them but they'd exit the screen before I could collect them.
Great job on the game overall, I really like the song!