Sound test:
After the game over screen, at the continue menu, press Up, Up, Down, Down, Left, Right, Left, Right, B, A.

Game genie:
2FC?86F?7FE - Re-enables the quite simple and partially non-functioning Debug screen. The values are uninitialized at start with this code. First two values represents the stage index and location respectively. Invisible option correspond to the sound player music index, but there are no code to start the music from there. The last visible options changes some game var, but it reinitialized when the game starting, so does not effect at all here.