Why does the tritone sound so unsettling? One reason is auditory roughness, the jagged, irregular quality of a sound that our brains often associate with danger, says Czedik-Eysenberg “Roughness is a particularly interesting audio quality—research indicates it can play a role in communicating danger [and is] a key feature in biologically salient alarm signals, such as human screams,” she notes. “But auditory roughness also plays a very important part in the perception of extreme vocal techniques used in metal genres. Guttural and harsh vocal styles, for example, are often described by listeners as brutal, monstrous, or demonic.”
But how we respond to sound isn’t just biological—it’s shaped by experience. “Our responses to sound arise from the nervous system that broadly speaking we all have in common, but context is everything,” says Victoria Williamson, a music psychologist and co-founder of the sound wellness app Audicin. “Some frequencies and sound textures are more difficult for the human inner ear and brain to process, a physiological clash that can trigger reactions from overstimulation to stress, disgust and even pain.”
“However,” Williamson adds, “our psychological reaction to sound is predicated on what we have been exposed to during our lifetime and the associations we have created. That is 100 percent unique to each of us.”
Back in 17th-century Europe, that exposure was changing. While medieval music prized harmony and order, the Baroque period embraced contrast and emotion. By the Classical era, it had appeared in works by Bach, Beethoven, and Wagner, among others, often to evoke drama or darkness. In Camille Saint-Saëns’s Danse Macabre, the tritone famously opens the piece with a musical scythe swing.
(Here’s how Beethoven went from Napoleon’s biggest fan to his worst critic.”