What makes scary music scary?

The science behind the spookiest soundtracks

Image via Max Pixel

A scary movie would be far less scary without its soundtrack. Close your ears during the most tense scenes, and they become almost boring. Take this recut of the trailer for The Shining as a happy family movie (“Shining”). It’s funny partly because of the voice-over, but mainly because of the happy Peter Gabriel music at the end. It works the other way around as well, as demonstrated by a fan-made trailer of Frozen as a horror film.

Music makes scary movies scary — but what makes scary music scary?

Daniel Blumstein is professor in the department of Ecology and Evolutionary Biology at UCLA. While studying marmots a few years ago, he noticed their distress calls were characterized by nonlinear noise patterns. He found this same pattern in other animals’ alarm calls, but also somewhere else: in the soundtracks of scary movies.

After analysing music from different movie genres, Blumstein discovered that scary movies often included high-pitched screams with a lot of noise. In this context, “noise” doesn’t mean “loud sounds”, but describes a disturbance in the sound — like radio noise. According to Blumstein, these noisy screams in scary movies have the same effect on us as animal distress calls: They evoke strong feelings, and we’re conditioned to find them disturbing.

In this TEDx talk, Blumstein explains how he collaborated with musicians to study the effect of nonlinear sound in film scores, and what this has to do with marmot screams.

Not all scary music is characterised by high pitched shrieking. Sometimes the use of minor chords and dissonant sounds is enough to evoke a spooky atmosphere. In the Middle Ages, one interval even started to be referred to as “Devil’s interval”. It refers to the tritone, or augmented 4th. This is the interval between A and E flat, for example, or between D flat and G.

The name Devil’s interval has taken on a life of its own. From the 18th century, people started talking about the interval that was forbidden in medieval times. The name makes it sound mysterious and occult, but it’s likely that it was only called “Devil’s interval” to warn people against using this odd chord that didn’t follow conventional rules of music writing.

The Devil’s interval definitely sounds unpleasant, and does a good job of making scary music sound scary. You can find it in the opening violin chords of Saint Saens’ Danse Macabre.

What makes it so uncomfortable to listen to? It can all be explained with physics. In any two-note chord, each of the individual notes produces a sound wave with a distinct wavelength. This sounds nice when those two sound waves meet again after a one or more of each of their wavelengths. This combination of two waves then creates a new regular pattern. But the two notes that make up the tritone or Devil’s interval have incompatible wavelengths. They don’t meet. Instead of creating a new regular pattern, they form a dissonant sound. This is explained in more detail in the article Where math meets music on the Music Masterworks website.

The irregular wave pattern formed by the augmented fourth chord. (CC-BY-SA by Adrien1018 on Wikimedia)

So, both high-pitched nonlinear noise and dissonant intervals generate feelings of unease that make them perfect for scary music. But that still doesn’t cover all aspects of scary music. What about the low drone sound used in the background of many films to generate suspense? What about the use of nursery rhymes or singing children to juxtapose fear and innocence?

We made these sounds scary by putting them in scary films in the first place.

In many cases, we have learned to associate certain music as “scary” simply because it’s often used in a certain way in films. Watch that Shining edited trailer a few more times, and you’ll start to think of Solsbury Hill as horror music. And Beethoven’s 9th isn’t inherently scary or unpleasant at all, but many film buffs associate it immediately with A Clockwork Orange whenever they hear it.

And in a way, this association also explains why high-pitched screams and dissonant chords sound “scary” to us. There are scientific explanations for why they sound unpleasant — they remind us of distress sounds, or they don’t form regular mathematical patterns — but unpleasant isn’t the same as scary. We made these sounds scary by putting them in scary films in the first place.

When you watch a scary movie this Halloween, pay close attention to the soundtrack and listen for nonlinear high-pitched screams, Devil’s intervals, and all the other tropes of scary music. And if it gets too much? Just mute the sound: it won’t be as scary anymore without the soundtrack.

Writer, science communicator, musician. Find more of my writing at Forbes.com, Undark, Nature, Nautilus, The Scientist, Hakai and other places.

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