Very cool idea, in a way pretty simple but still efficient, even if I suck at rhythm games (I think you can call this a one), I did get few tries in before absolutely just accepting the fact that anything involving rhythm is my doom.
Only real like suggestion I have is that if this game is developed/updated later, I'd say make the keymaps not hardcoded/something the player can customize. Players might have different region keyboards (like I for example have Finnish) and the note for ";" is actually my "Ö" and my ";" is located under my keys for "K" and "L", so... um yes that caused huge initial confusion, it's even confusing to explain lmao. But yeah, this is a nitpick in the end, I realized pretty quick why the notes weren't registering.
Regardless of that, good work on this! :D