Really cool idea. I like when the music is attached to what happens in the game, and I really like how you can control the music to influence what happens in the game. The first two times I tried, it felt really hard, since I didn't realize I was supposed to create the drum loop at the start. I think it would be nicer, instead of front-loading all the drum loop creation, if you could add an extra beat or two every level, so you get the feeling of levelling up, and so you can ramp up the difficulty and the player's abilities at an even rate. It would also give variety to the music, if it changes every level as you add to it. If you do a future version of this, I'd even go past the drum loop, and maybe layer the music together, so you can add the music in over time and make that also go from a basic bassline or something to a sonic wall. The concept kind of reminds me of how some games, like Sunset Overdrive, layer in their music based on the action (just in this case, it's the other way around, which is really cool).