The iconic shower scene in Psycho was originally supposed to play out without music. Instead composer Bernard Herrmann created “The Murder”: as the killing transpires, violins shriek and scream along with the victim.
The film’s director, Alfred Hitchcock, reportedly later said that “33 percent of the effect of Psycho was due to the music.” In most horror flicks, the emotional current that carries the viewers is the music, which accelerates their anticipation and heightens the jump scares. It’s not just screaming violins, either: undulating synthesizers drive John Carpenter’s Halloween; “evil” clarinets underpin Hereditary; a recording from the 1930s enhances Get Out.
Studies have shown that certain fearful music activates the brain’s alarm-response system. So what is it that makes some music sound scary? Psychoacoustics researchers have found that some auditory features that are common in horror music are inherently frightening. The most obvious way music can scare us is by literally imitating screams, like Psycho does. Here, the instruments mimic a quality of human screams called roughness. When we scream, we press a high volume of air through our vocal cords, causing them to vibrate chaotically. This creates a sound wave with an amplitude that fluctuates rapidly, which our ears and brains perceive as rough or harsh.
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To imitate this musically, violinists must push the limits of their instruments. “They’re pushing into that string, literally—just pushing the capacity of the instrument. You feel the whole instrument almost resisting the sound,” explains Caitlyn Trevor, a music cognition researcher and founder of the sound design consulting company SonicUXR. In a 2020 study, when Trevor was a researcher at the University of Zurich, she and her colleagues studied horror movie soundtracks and found many of these screamlike musical cues.
Rough vocalizations seem to have privileged access to our brain. In a study published in May, scientists found that the sound of a distant scream could elicit a response from the brain even in the deepest stage of sleep. When you hear a scream, it quickly activates the amygdala, a brain structure involved in processing danger, and it can trigger a cascade of alarm reactions in the nervous system. The short burst of sound may also trigger our startle reflex, which bypasses higher-order brain regions and goes straight to our body to help us respond fast.
Most horror music is not about directly inducing terror, however. Those moments of auditory release are usually preceded by long, roiling tracks that build suspense. “There are actually two very different types of music that are ‘scary’ or ‘fearful,’” Trevor explains. In 2023 she co-authored a study examining the musical differences between these two types of horror movie tracks. Participants rated the emotional effects of different excerpts. The results showed a distinction between anxiety-inducing and terrifying music; the two types “sometimes have completely opposite acoustic features,” Trevor says. Where terrifying music was loud, brash and dense (a chorus of screamlike string instruments from Midsommar was ranked the most terrifying of all the examples in the study), anxiety-inducing music tended to be more varied. Here is where composers have the most room to play, using subtle auditory cues that are biologically ingrained to keep listeners on edge.
For example, some horror movies use (or are rumored to use) very low-frequency sounds on the border of human perception to give an intangible sense of doom. “Certain sounds mimic danger out there in the world,” explains Susan Rogers, a music producer and music cognition researcher at Berklee College of Music. “A low rumble is something we have evolved to be alert to,” she says—perhaps signaling a stampede, a storm, an earthquake or something else dangerous in the environment.
Fast tempos, especially ones that sound like a heartbeat, can also put us on edge, Rogers explains. In the theme from John Carpenter’s Halloween, a low thudding that is reminiscent of a heartbeat drives the music forward. “A predictable rhythm gives you a sense of momentum and that [the filmmakers are] leading toward something,” Trevor says. The listener doesn’t know where the music or the story are going, but they feel relentless and inevitable.
More commonly, though, horror movie music builds suspense by making itself unpredictable. Suspenseful music, Trevor found in her 2023 study, often keeps us on edge by sprinkling in bits of sound in unexpected places. Sometimes these scores use an unpredictable or lopsided beat, dropping notes here and there, to prevent the listener from settling into the rhythm, she adds.
“The soundtrack and the sound design are integral to letting you predict what’s going to happen, so sound designers in horror movies can use the technique of violating our predictions to get us to experience fear,” Rogers says. The brain is a prediction machine, and it allows us to tune out expected or constant noise. “Whether it’s a car engine or a rainstorm, we know how it’s going to go, so we move our spotlight of attention onto other things,” she continues. If you hear footsteps coming up the stairs, you might predict that they’ll continue until they reach the top; but if they stop halfway, you become alert. These sorts of “prediction errors” activate the amygdala and a memory-forming region called the hippocampus.
But some of the most frightening features of horror movie music are culturally learned and might not be inherently scary. For example, composers often build tension in music using dissonance, when the pitches of two or more notes seem to clash against one another. The idea that some harmonies are inherently dissonant has some truth—if two notes are too close together in pitch, the soundwaves can interfere, causing a “beating” pattern that can be unpleasant or grating on the ear. “But only at the most basic level is that universal. Above that, the musical concept of consonance and dissonance is entirely learned,” Rogers says.
Other harmonies that were once assumed to be inherently dissonant—for example, the so-called devil’s chord, or tritone, which is used often in horror movies—are perceived differently across different cultures. A 2016 study found that the Tsimane’ people of rural Bolivia, a group whose music does not use harmony, rated the tritone and other “dissonant” intervals as equally pleasant as “nondissonant” intervals.
Some of the most creative horror movie soundtracks play on our cultural expectations to create a feeling of unease or fear, Trevor adds. Many horror movies make use of old records, which have a warbling sound quality and often feature an old-fashioned way of singing that sounds odd to our modern ears. This can create an uncanny valley effect—something that should be familiar is instead subtly strange. “You know what it is, but there’s something wrong with it,” Trevor says. “It’s not right. And that is really disturbing at a deep level.”
