Music lives deep within us, in the marrow of our evolutionary bones, tapping into “this very primitive system,” says British musicologist John Deathridge, “which identifies emotion on the basis of a violation of expectancy.” In other words, our brains are predisposed to hear certain combinations of sounds as soothing and others as disturbing. When we plot those sounds on a staff, we find one of the most dissonant, yet intriguing, combinations, what can be called an augmented 4th or diminished 5th but isn’t quite either one. But it’s much better known by its medieval nickname, “the devil’s tritone” (or “devil’s interval”), a sequence of notes so sinister, they were once banned in the belief that they might conjure Lucifer himself…. Or so the story goes.
The truth is less sensational. “To the chagrin of many a musician wanting to tap into a badass rebel streak in music’s DNA,” James Bennett writes at WQXR, “there aren’t any records to suggest any rogue medieval composers took a hike to Perdition after using this spooky, devilish interval.” In other words, no one seems to have been tortured, imprisoned, or excommunicated for a musical arrangement, all internet assertions to the contrary notwithstanding. But the association with the devil is historical. In the 18th century, the tritone acquired the name diabolus in musica, or “the devil in music,” part of a mnemonic: “Mi contra fa est diabolus in musica” or “mi against fa is the devil in music.”
If you’re already versed in music theory, you’ll find this technical explanation of the “devil’s interval” by musician Jerry Tachoir helpful. In the video above, bass player Adam Neely debunks the myth of the devil’s tritone as an actual curse. But his explanation is more than “one long, ‘Um, Actually,'” he says. Instead, he tells us why the tritone is a musical blessing, and was thought of as such a thousand years ago. His explanation also gets a little technical, but his visual and musical demonstrations make it fairly easy to follow, and if you don’t absorb the theory, you’ll pick up the true history of the “devil’s tritone,” beginning with the Greek thinker Aristoxenus of Tarentum, one of the first to write about the uncomfortable dissonance of a note sitting between two others.
The tritone is what musicologist Carl E. Gardner called a “dependent” chord, one characteristic of tension. We may not register it consciously, but it primes our brains with anxious expectation. “The reason it’s unsettling is that it’s ambiguous, unresolved,” says Gerald Moshell, Professor of Music at Trinity College in Hartford, Conn. “It wants to go somewhere. It wants to settle here, or [there]. You don’t know where it’ll go, but it can’t stop where it is.” We hear this irresolution, this “devil” of musical doubt in compositions ranging from The Simpsons theme to the chorus of Pearl Jam’s “Evenflow” to Camille Saint-Saëns’ “Danse macabre,” a piece of music that may not actually conjure evil, but sure sounds like it could if it wanted to.