Undertale Wiki
For the prologue of Undertale, see The War of Humans and Monsters.

Long ago, two races ruled over Earth: HUMANS and MONSTERS.

Opening Cutscene

Once Upon a Time is the 1st track in the Undertale Soundtrack and in the Undertale Demo OST. It plays during the introduction sequence of the game on every launch. Its opening theme is the primary leitmotif of the game.

Like many of the tracks in Undertale, "Once Upon a Time" is stored at a different speed in the game's files. However, unlike other tracks, the OST version has a lower pitch compared to the version heard in-game.

In the Undertale Demo OST it plays at the in-game speed.


  • This track is used two times in the game; the second is during the fight with the final boss of the Neutral Route after the boss closes the game. Upon relaunch, the track plays normally while a fake version of the original intro is shown before "glitching".
  • This track is loosely based on the track Mother Earth from the game EarthBound Beginnings.
  • 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.
  • 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.
  • At the start of the game trailer for Undertale, there is a section of music before the title is shown which sounds similar to Once Upon a Time.