The whistle comes from the theme to The Good, the Bad and the Ugly, the 1966 western directed by Sergio Leone with music by Ennio Morricone. The melody became one of the most famous sounds associated with western standoffs, and short edits of the whistle spread widely in memes, video compilations and reaction clips. It is still used because a tiny excerpt immediately suggests suspense, a duel, or a playful exaggeration of conflict.