Gene's Rock-a-Bye is the best song. That and the main theme/end theme/whatever.
This game was really fun. Many people say the game is "broken" but understand by broken they mean it takes longer than five minute to learn how to play, which is way longer than their attention span allows for.
The game was aggravatingly hard at times, but still a fun game. The samurai master boss was a particular pain in the ass that I think I could only manage to repeatedly play because I loved his battle music.