Great work. A big chunk of feedback coming through!
Above all, I think this is a plain platformer with a music theme to it. I think in a platformer where your vision is limited, you're opted to use sounds to navigate more - and I assume that was the original idea, but it came short of that idea. The player can't see much and the levels are linear, which means that you don't really need to listen to audio to look for clues, but just gotta be careful of pit falls and rising triangles. Like one of the players commented, foreground and actual areas where you can step are blurred. I think foreground elements can be colored differently solidify an expectation from the player.
Mechanic wise, I didn't know what collecting the music notes did. Did it brighten up my screen, or change the music in the background?
Some of the SFX were not standing up to the rest of the game. I really couldn't stand that death sound. Yes, you do want to discourage the player from dying in your game, but never use this kind of audio for death that can happen really often in a game like this. I really think you could use a shorter, and duller sound for narration text. The sound alone is painful to the ear, especially when you try to skip narration.