The sound comes from the theme music of The X-Files, the science fiction television series that premiered in 1993. Composed by Mark Snow, the theme became famous for its eerie whistle-like melody and minimalist electronic atmosphere. Over time, short cuts of the theme spread beyond the show into internet memes, reaction edits and parody videos. It remains popular because a tiny fragment is enough to signal mystery, aliens, hidden truths or an obviously overblown conspiracy joke.