The Character Select Music is O_CHRSEL,
The Continue Music is O_CONTSC,
The Level Clear Music is O_LCLEAR,
The Drowning Music is O_DROWN,
The Speed Up Music is O_SHOES,
The Invinciblity Music is O_INVINC,
The Extra Life Music is O_XTLIFE,
The Game Over Music is O_GMOVER,
The Title Screen Music is O_TITLES,
The Mario Invinciblity Music is O_MINVNC,
The Credits Music is O_CREDIT,
The Intro Music is O_READ_M, and
The Multiplayer Score Screen Music is O_RACENT.
That should help you know what to rename your music to if you want to replace any of these tunes.