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When you hear it, you know something bad is probably about to happen.

For almost a century, film composers and sound designers have used a similar sound to create a tension in movies: that long, eerie, sustained tone (or cluster of tones) known best as “the drone of dread.”

Drones can be low- or high-pitched, subtle or cacophonous, and made with a variety of instruments and electronic tools, but the effect is always the same. It instantly produces a sense of anxiety, as if out of thin air.

“It’s the sound of dread,” Neil Lerner, a musicologist and professor at Davidson College, told Quartz. “And that’s something that I think triggers fear in all kinds of creatures.”

Drones in music can be traced as far back as the 19th century to composers like Richard Wagner, who wrote 10- or 15-minute-long sustained notes into his compositions. According to Lerner, the drone probably appeared in a film for the first time in 1931’s Dr. Jekyll and Mr. Hyde.

From there, you can hear it in everything from 2001: A Space Odyssey to The Thing to, more recently, The Dark Knight and The Social Network. This week’s episode of Game of Thrones, in fact, had an obvious drone toward the end that signaled a character’s impending doom.

While there are drone sounds throughout the entire history of film, they tend to pop up most often in eras of heightened global anxiety, like during the Cold War and, well, right now.

Quartz News is a weekly video series bringing you in-depth reporting from around the world. Each episode investigates one story, breaking down the often unseen economic and technological forces shaping our future.

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