The melody comes from Five Nights at Freddy's, the indie horror series that began in 2014, where a wind-up music box is tied to animatronic characters and moments when the player is most vulnerable. Its tune is a version of a traditional clockwork melody, played slowly enough to sound innocent and threatening at once. As let's plays, fan games and remixes spread across YouTube and social media, the sound became shorthand for FNAF itself. It remains popular because a few notes instantly signal creeping danger without needing any context.