Pac-Man SGB / SGB2 Super Game Boy ~ Calling Unused Sample Playback (Part 1 ~ Snare 1)
If you wanted proof that all the sound effects stored in the Super Game Boy BIOS that are used for various in-game GB games effects are actually a song BGM / composition. E0 is the instrument call function.
Set palette swap X button sample (requires restart)
869FCE??
869FD9??
00FA39?? - Set pitch (00-03)
Unused samples:
34 - Snare 1
35 - Snare 2
This is actually a very unusual situation. While there are technically unused samples stored in the SGB, they were intended to have been used by games that offered custom SGB soundtracks. A few games did actually use the samples.
The SGB2 does use the snare 2 instrument in the credits theme. Also, it is worth noting that Game Boy games could upload custom 16-BIT (near CD-quality) samples using the sod directory and they can be played using this method. Donkey Kong 94 is one such example with Pauline's scream (sample 02).
Unused SGB/SGB2 samples:
NOTE: Set sample to 40 for null / mute sample playback in either address (869FCE40), then set the sample you want to play in the other address because there is a slight echo effect (achieved by using two SPC700 channels instead of DSP setting.)