I'm gonna make it simple and say Clock Town Day 1. I feel like it's the perfect transition music from OoT into MM. Also, the latter days' songs are much too fast although I do recognize that is done for effect to achieve tension as the moon approaches to destroy Termina.
Well, favorite song in the game: Woodfall Temple (don't worry, STT is right behind it).
Favorite ocarina song: Goron Lullaby, with Elegy of Emptiness right behind.