Music can be selected on a room-by-room basis and is editable in SMILE on the right side of the main window under the “Other” tab. The first number in the list below is the Collection value and the second value is the Play value.
00 00 = no change 00 00 = no music 00 01 = Samus appears clip 00 02 = Item aquired clip 00 03 = Elevator music 00 04 = Hallway before the statues / Continue music 00 05 = No change. If entered from a ## 00-04 room, switches to ## 00 06 = Retain's previous room's track, but plays the 06 version of it 00 07 = Mute, game crashes when you enter a door 03 05 = Title screen music 03 06 = Title screen music after Start is pressed 06 05 = Empty Zebes w/ Thunder 06 06 = Thunder alone 06 07 = Empty Zebes w/o Thunder 09 05 = Space Pirate music 09 06 = Statues before Tourian 0C 05 = Samus's Theme 0F 05 = Green Brinstar Fadein 12 05 = Red Brinstar Fadein 15 05 = Upper Norfair 18 05 = Lower Norfair 1B 05 = Eastern Maridia 1B 06 = Western Maridia 1E 05 = Tourian 1E 06 = No music 21 05 = Mother Brain fight 24 05 = Boss fight (Ridley) (KEJ: Draygon uses this. Ridley uses 24 04) 24 06 = Music before fight w/ Bomb Torizo 24 07 = Escape music 24 80 = Ridley on Ceres (KEJ: Added 5/3/05. No idea what the 80 does) 27 05 = Boss fight (Kraid) (KEJ: This is used by Crocamire, not Kraid) 27 06 = Music before fight w/ Kraid (KEJ: *This* is used by Kraid, and Phantoon) 2A 05 = Miniboss (Spore Spawn) (KEJ: Botwoon too) 2D 05 = Colony to Zebes 2D 06 = Ceres 30 05 = Wrecked Ship asleep 30 06 = Wrecked Ship alive 33 05 = Zebes goes boom 36 05 = Intro music 39 05 = Death 3C 05 = Credits 3F 05 = "The last metroid is in captivity" 3F 06 = No music 42 05 = "The galaxy is at peace" 42 06 = No music 45 05 = Boss music (Kraid) (KEJ: Actually, Metroid's music, called indirectly. I doubt Kraid uses this) 45 06 = Music before fight w/ Kraid (KEJ: Actually, this is used in Tourian, for the blue Sidehoppers) 48 05 = Samus's theme
Thanks goes out to Kejardon for creating the list. It can be found in it's original form in this document in his sub-domain located on Zophar's Domain.