Sound Test

Sound Test is a mode in most games that allows music and sometimes sounds made in the game to be played.

Super Smash Bros. Melee
In Super Smash Bros. Melee, Sound Test is unlocked after unlocking all of the characters and the stages.

Metroid: Zero Mission
In Metroid: Zero Mission Sound Test is unlocked after beating the game on all the difficulties on one file.

Kirby Air Ride
In Kirby Air Ride, the player can only listen to a few songs at first. The rest of the songs must be unlocked.