I agree with Akira. The tunes themselves are pretty good actually, but it feels like they belong to a different genre (like a space shooter perhaps?). I think a more atmoshperic soundtrack would compliment greately the dark tone and visuals. Even some sort of a soundscape or ambient would fit perfectly imho. Obviously having only 16k to work with is an important bottleneck but chiptune can be dark and eerie alright, so it's not an issue of available resources or samples
On the other hand it's rather stereotype to expect something moody and downbeat just because it fits the know mold. And since the above mentioned tracks are nice and all it's not that they hurt the game, they just push it in a different direction (which may be good or bad, depending on your view point and expectations).
One extra note I'd like to point, unrelated to music. I'm not sure if this is final or not (or if it is in your todo list for a future optimisation) but from what I've seen from the latest video and older ones, the main character seems to stuggle to pickup up stuff sometimes. Perhaps I'm not getting something, so I'd like to ask. Is there a pickup mechanic involved? Like you need to press a key to pickup items or you pick them up as you touch them, or pass by them, or..?