I never knew about the debug code.
I checked it out and I've heard every one of these tracks in the actual game. Here's the track list:
0: Initial track
1: Last world of the normal game
2: First world of the extended game
3: Last world of the entire game
4: Boss soundtrack
5: Final boss soundtrack
6: World Clear music
7: Secret room track
8: "Fast" initial track
9: "Fast" last normal world track
10: "Fast" first world of extended game track
11: "Fast" last world track
12: Bonus game
13: Character cast ending
14: Proper ending track
15: Game Over track
16: High score name entry track
17: Used when three of the square symbol things appear at the top of the screen
18: Heard when the regular game ends
19: Heard when you press the start button on the ttle screen
That should cover them all.