Boot music

The boot music is the famous jingle played during the eyecatcher animation on system startup, and often seen again during attract sequences.

The special sound code 2 is used by the animation routine in the System ROM to request it. It's up to each game's sound driver code to actually play it.

Many games remap and/or add instruments (different instruments in Blue's Journey, drum loop in Neo Bomberman for example), but all games seem to use the same exact melody, which was probably SNK's requirement.

The original music is FM only and uses all 4 channels as 2 pairs of "echo" channels (2 melodies only, each being played with a slight delay). It's played at 192 BPM and uses down to 1/32 notes.