This looks so cool. First of all, thanks for bringing an already amazing game back to life and making it even better a lot of really cool things going on with this code and I really like what your doing.
Maybe for the music you could make it more like white water where it starts off simple and then as you progress through the mode it gets more and more involved? The problem I see is finding a song that does that well and doesn’t start off “too slow” have you considered scoring your own music for it? Or having someone in here do it?