As a hobbyist piano player I really enjoyed it. It was somewhat confusing to use the keyboard in reverse, with the high pitch notes on the left and it took me a bit of time to get used to it. Thankfully, you included the sections with a single note that help orient myself. In the end, this was an oddly engaging game and I spent way more time on it than initially anticipated. I must say that it would probably have been better to get your own assets and perhaps disconnect a bit from the source scene... But that's just an opinion. Nonetheless, the cutout animations are really good and add to the feel of the game. Overall it's a very satisfying game. I very much enjoyed getting any sequence right. But unfortunately I could not finish the game.
As a final note... Don't give up on Godot so easily.