The bird bard himself!
Overworld is iconic and quite well written, though maybe a bit overused now. Underwater is pretty good too. Underground is a bit overly simple in the original game but it could be worse. Castle theme's not all that great. Peach's theme is good but would be way better if they had been able to include the whole thing as they had planned (which they succeeded in doing in Lost Levels). I vote for Overworld and Underwater.