Arcade Classic No. 4: Defender & Joust

Planned Super Game Boy Soundtrack
A Super Game Boy soundtrack was planned and was ultimately ended early on during development. The SOU_TRN command located at is the last remaining piece of evidence. 49000000000000000000000000000000

While it is not technically useful, you can use Game Genie codes to load the unused SOU_TRN register command along with the initial commands. This will hang the Super Game Boy BIOS indefinitely because SNES APU music score and data is not mapped.

Unused Music
There are three "classical" pieces that are unused. Could have been intended for anything. Game Genie codes (where "??" is one of the following) will play the selected song at the Joust or Defender title screen:







Disabled Nintendo Logo Sound
There is code that would load a sound effect for the Nintendo logo. A short jingle was likely intended to play. Game Genie code will play any selected sound effect. There is also code that would fade out BGM.