This game really slaps! The gameplay is certainly creative, and the looks and music also are really juicy. The main character is adorable, reminds me of a void creature of Hollow Knight but instead of insect shells he uses a cape and it looks awesome xD The menu is also a really nice touch, great work!
The total bane of game jams are the balancing issues, which every game seems to suffer unfortunately. And for Tune Town, the beat is certainly on time, but the window to do actions really feel too short, especially when you have to perform two actions at the same time. Some sequences can turn out to be really hard at times, like pressing the up arrow while there's an enemy in front of you, so you have to really keen on pressing up and right, without counting the boss that lurks behind you.
Speaking of the boss, was he supposed to deal any damage? At first I was very cautious to not let him get close, but once he indeed got close... He stayed at my face and everything went as normal.
The tutorial could also quickly explain basic actions such as jumping and throwing boomerangs (which I had to look to the controls again to realize that I could also shoot them backwards).
Also, the character can sometimes get stuck from a lower platform to the really tall narrow building, and from there the game runs as usual but the player gets dragged behind. Seemed funny at first but I had to close and reenter the game to play all over again (Maybe a pause menu with a restart could be a cheap help with problems with these).
The windows that stay underneath the player served as a good indication for me on when to jump, but I didn't kind understand when they turned on or off and confused me some times, maybe they could light up when the player passes through them as a visual indication of actions?
And finally, the clapping sound for feedback for the score arrows are a nice touch, but I don't feel the same for jumping and throwing boomerangs. I mean, there are sounds for throwing boomerangs, but they do not fit nicely with the music it seems, a rapid woosh sound would be better off I think. And for jumping there's no sound, a really basic jump SFX would be enough to tell my ears that I executed it right. Anyways, you could take inspiration on how osu! and similar games tackles on these things: