A shooter based on music theory note values is such a bizarre concept, I love it! It reminds me of some of the wacky guns you can get in Enter the Gungeon. I highly encourage you to explore this idea further, because there's a lot you can do with it, and you've already implemented it in lot of creative ways. Personally, I would love to see a game like this when an adaptive soundtrack, you know, because it's music-themed, but of course that's not realistic for a jam game and the music was pretty great anyhow.
I would've preferred if there was a tutorial that showcased all of the different note values and expressions and what effects they have, it would've made the game more engaging having a further grip on what's going on.
Anyway, very whimsical and very fun, great work!