The whistle comes from the main theme of Sergio Leone's 1966 film The Good, the Bad and the Ugly. Ennio Morricone composed the score, and Alessandro Alessandroni performed the theme's memorable whistling. The music became closely identified with Spaghetti Western imagery and the film's tense confrontations. Short excerpts later spread through television, online videos, memes, and parody edits, where creators use the melody to frame everyday encounters as serious duels. It remains effective because audiences can recognize its Western mood almost immediately, even from a very brief clip.