Once Upon a Time

Once Upon a Time is the first track in the Undertale Soundtrack. It plays two times in the game: during the introduction sequence of the game on every launch, while the second is during the fight with the final boss of a Neutral Route after the boss closes the game. Upon relaunch, the track plays normally before leading to a fake version of the original intro before "glitching".

It is the primary leitmotif of the game. Like many of the tracks in Undertale, "Once Upon a Time" is storied at a different speed in the game's files. The version in the file mus_story.ogg is stored at 100/91 (1.(098901)x, 9.(890109)% increased) speed. To normalize this, the game plays it at 91% (9% reduced) speed. However, unlike other tracks, the OST version has a lower pitch compared to the version heard in-game. To get close to the pitch heard in-game from the OST version, increase its pitch by 0.455 semitones, or the other way around: to get close to the OST version from mus_story.ogg, reduce the pitch by half a semitone, then play at 0.91x speed.