Tetris (Arcade, System 16)
The arcade Tetris was Sega's first take on the massively popular puzzle game, which introduced a number of gameplay rules that still survive in some form to this day.
Sound code 91 is a short tune which is never heard during normal gameplay. Purpose unknown, although its length might fit with some form of continue screen. The fadeout is actually part of the track; it does not loop in-game.