The game seems to be running at a very low FPS which makes everything look stuttering. It hurts a lot when it comes to rhythm games as they are strict on timings. Art looks well individually though.
In terms of gameplay, it gets a bit unfair later on as I don't really have enough time to move the cursor to the right position for a few notes. And again, the stuttering also affects the control quite a bit. If this can run at 60 fps smoothly I guess it's going to be a completely different story. But overall I think it's a solid design that is fairly challenging.
I don't know if it was just instruments but sound quality seemed quite low even for free assets, and the volume suddenly went up in the middle. As a rhythm game you may need something better, but for a 3-day jam I think it's okay.