The theme was composed by Mark Snow for The X-Files, the science fiction television series created by Chris Carter that premiered in 1993. Its whistled melody and echoing effects were designed to feel unsettling and unanswered, matching stories about FBI agents investigating paranormal cases. As clips moved online, the music escaped the show and became shorthand on forums, edits and social video for anything unexplained. It is still used because a few notes instantly tell viewers to question what they just saw.