What makes eerie music so chilling?

What is it about a haunting piece of music that immediately sends chills down your spine? While you might not be able to explain it in technical terms, you certainly recognize fear when it hits your ears. The jarring sounds, discordant harmonies, and abrupt high-pitched tones all work together to unsettle us. But what’s the reason behind this? Are these sounds naturally terrifying, triggering a primal reaction, or is it something we’ve learned to associate with fear over time?

The truth likely lies somewhere in between. Music theorists have long pinpointed specific note combinations that are particularly unsettling, even if the exact reason for their dissonance remains unclear. The tritone, for instance, consists of two notes separated by three whole steps (such as F and B) and was historically referred to as diabolus in musica (the devil in music). Throughout history, certain note pairings, like the tritone, have been deliberately avoided to prevent any association with negativity or fear.

There’s also an element of fear-by-association that doesn’t necessarily rely on dissonant notes or musical structure. Certain pieces of music remain terrifying today due to their historical context. The Dies Irae, a Gregorian chant with just eight notes and dark, apocalyptic lyrics, still evokes fear even among those who don’t understand Latin or know its origins in Catholic funeral masses. Similarly, Bach’s "Toccata and Fugue in D-minor" wasn’t widely regarded as frightening until its use in films like "Dr. Jekyll and Mr. Hyde" and "Tales from the Crypt."

However, Daniel Blumstein, an evolutionary biologist at the University of California, Los Angeles, published two studies (in 2010 and 2012) suggesting that our reaction to "scary" sounds is deeply rooted in biology. Composers and filmmakers, he argues, have been exploiting innate emotional responses when crafting eerie music. Blumstein and his team observed that nonlinear chaotic noise—harsh, unpredictable sounds made by distressed animals to alert their parents—also triggers emotional discomfort in humans. These discordant, jarring sounds are unsettling to our ears. Sound familiar?

The team analyzed over 100 movie soundtracks across four genres—horror, drama, adventure, and war—and found that nonlinear sounds play a crucial role in scenes designed to evoke fear and unease. Think of classics like "Psycho," "Jaws," "The Shining," and "The Exorcist." Even as early as 1933’s "King Kong," sound engineers used real animal cries and screeches to instill terror in audiences.

So, the next time you’re gripping your seat during a tense moment in a horror movie, pay close attention to the nonlinear sounds in the soundtrack. Will knowing that your primal instincts are being manipulated make the experience any less terrifying?