Nice idea, I like it! Also the fact that you're playing a human cursor is very fun.
I must say that the platforming was a bit frustrating, I felt like I had to focus a lot for my jumps, as the notes are very close to each other (both vertically and horizontally), it's very easy to get stuck on a jump, fall, get killed, and being reset on the left. Even worse when that happens on the right part of the screen, because you respawn on the left, and the playing marker kills you on spawn. I know you can loop from right to left, but then you have to run all the way to try your jumps again, which can become annoying quickly. At least the respawning is quick so that's not that serious, but definitely something I would improve if I were to work on the game. And that leads me to another thing, which
I feel like the game is more of a platformer than a music/rhythm game, which tricked me a little bit because I was expecting being able to do some composition using the notes by jumping on them or something, and eventually I was just focusing so much on platforming and not dying that I wasn't listening that much to the music. Which I think is a shame as it's called "Midi Madness".
I guess I'm being critical because I'm a developer and a musician, and while I really love the initial idea of the game, I may have been expecting something and was kind of frustrated (and that's my problem, not the game's). But, it's not my game, and overall I believe that it's a great entry and a cool take on the theme!
Looking forward to your next version with that second level!