“Diabolus in Musica”

“Diabolus in Musica” is an album by the metal band Slayer, but the group took the title from another place — an alleged accusation of the devil residing in music itself: not just any music, but a certain nefarious sound.

This sound is known to music theorists as a “tritone” and it appears in a musical interval that spans three whole tones. “The flatted, or diminished, fifth” or the “augmented fourth,” was thought to have made up an evil chord which 18th century composer Georg Philip Telemann called “Satan in music.” In fact, a number of musicians from the 1700s claimed that, back in the Middle Ages, the Catholic Church had banned the notes because of their association with the devil. However, these accusations appear to be unfounded because no Medieval sources attest to such a regulation.

The Church was likely to have discouraged the flattened fifth for other reasons, however. As early as the 9th century this tritone was considered a problem in music, and that is because of the quality of its sound, which seemed restless and dissonant. In fact, my very untrained ear (and yours too, likely, whether trained or not) does find it a note of transition, not of completion, simply because I have been surrounded by the musical tradition based on the octave.

Eventually, Western musicians started to embrace the ‘cord of evil’ because of these properties. Giuseppi Tartini (d. 1770), for instance, wrote one of the most challenging virtuoso violin pieces featuring it center-stage in his sonata “The Devil’s Trill,” even claiming the devil played it for him in a dream. And Camille Saint-Saëns also used it in his “Dance Macabre,” to imagine skeletons coming alive in Halloween. And then, there’s the album by Slayer.