Interesting concept, I feel like there's potential but 48h is definitely a bit short to fully develop it. As others have said, maybe something akin to the musical levels in Rayman Legends would work better?. The balance between leading the players and giving them creative liberty seems hard to find!

That's an interesting twist on the platformer genre, but I think the execution could use some tweaking (which is hard to get enough of in a game jam).

For example, you could try to make the levels in a way that helps to play a decent melody. Or maybe pivot the game so that it's no longer a platformer, as suggested in another comment.

As for the implementation itself, the controls felt a little floaty.

Nice visuals though. Good job!

Like making music while playing, but it makes holding a key a bit annoying. Also jumps are a little unforgiving for my taste. Could be really cool with more time put into level design to "force" players into making a good music

In theory a very cool idea, saving the file you made is such a genius addition! But it doesn't particularly feel like the average person will make good music from this, which is a shame because if the level was designed differently and the other keys had functionality instead of existing as different notes there's really a lot of potential here to make a great game!