I don't have much rhythm game experience, but I found this game a bit frustrating; I felt like I was getting dinged for prompts I correctly responded to. Maybe it's an issue with telegraphing, and giving the player a clearer indication of exactly how they messed up a prompt would help? I have a hunch that my problem relates to timing, and I think giving the player some extra feedback could help.
When my prompt feels like it's graded correctly, though, I find it quite fun and satisfying. The art is pretty nice, too!