just saw a melee build here:
i don't mind the corruption sound. it makes me feel that i have done something even the game didn't expect me to do.
for the melee build being op, how about making the combo attack alternate between bars? i.e. for one bar activate activate the combo and deal constant damage and invincible and sorts, and on the next bar return to a more vulnerable state, and then back to "i haz the powaa!" mode
also, to balance melee being so op in the early game, you should put more shooting enemies once the player gets 8 notes to play. these shooting enemies should pierce the melee blob so that the player need to move around to dodge them