Frequently referred to as the “Devil’s music” by religious fundamentalists, rock and roll was born from a music genre indelibly linked to the diabolical: the blues. Robert Johnson, one of the greatest blues guitarists who ever lived, sold his soul to the Devil at a crossroads in exchange for supernatural talent (or so the story goes). However, the association of rock and blues music with evil goes even deeper, and is more technical, than mere stories of making deals with the Devil. Rock and roll inherited its four-on-the-floor time signature and syncopated rhythm from the blues, and it just so happens that nearly every chord in the blues is a dominant 7th, a chord going from the 3rd to the flat 7th, which is what is known as a tritone. What’s so evil about that? Well, the myth is that singers and composers in the Medieval ages were forbidden from incorporating tritones into their music and that the Catholic Church actually banned the tritone for being diabolus in musica, or “the Devil in music”! That’s a great story and works well at establishing devilish respectability in the arms race of evil wherein each heavy metal band tries to one-up the other. But is there any truth behind the myth?

According to Encyclopedia Britannica, the tritone, otherwise referred to as an augmented fourth (e.g., F-B or C-F#) or as a diminished fifth (e.g., B-F or C-G ♭) is an “interval encompassed by three consecutive whole steps, as for instance the distance from F to B (the whole steps F-G, G-A, and A-B).” Just listening to examples of a tritone, whether it’s Tartini’s “Devil trill sonata” in G minor or “Maria” from West Side Story or “Black Sabbath” by Black Sabbath, provides a clue to how the tritone earned its evil reputation. The tritone is a dissonant interval; it just doesn’t sound “right” to the human ear. As John Sloboda, professor of music psychology at London’s Guildhall School of Music and Drama, explains:

Our brains are wired to pick up the music that we expect. So, when we’re listening to music, our brain is constantly trying to guess what comes next. And generally, music is consonant rather than dissonant, so we expect a nice chord. So, when that chord is not quite what we expect, it gives you a little bit of an emotional frisson, because it’s strange and unexpected.

As can be deduced from the previously mentioned examples, the tritone is often employed by composers, usually to evoke a sense of unease and dread (e.g., an A-E flat in Saint Saen’s Danse Macabre) or to serve as a musical leitmotif for the villain (e.g., another A-E flat tritone in Beethoven’s Fidelio). In truly Satanic fashion, tritones can also be used to represent carnality, as composer and High Priest of the Church of Satan, Peter Gilmore, explained to me: 

The other aspect of this interval is its sense of longing to resolve its dissonance, hence it also symbolizes desire, yet another aspect of carnality that “spiritual” music would tend to avoid, unless it could be used as a desire to be one with the divine. Composers have long used it to conjure both uncertainty, tension, and desire. In his score for West Side Story, Bernstein uses it deftly for both meanings. The opening theme, whistled in the film score, begins with the interval of the tritone—creating a sense of tension, which matches the scenario of the rival gangs that is the basis for the story being told. It is also the interval that is infused in the song “Maria” where it represents love, longing, and desire.

Besides lending itself well to evoking lascivious feelings and unholy ruminations, there is a more fundamental reason ecclesiastic authorities shunned the usage of the tritone in musical composition: dissonance inherently contradicted the Christian worldview. According to Maestro Gilmore:

European ecclesiastical music was intended to represent an ordered universe as so brought into being by their deity, and thus the inherent ambiguity of the tritone served as a representation of doubt and uncertainty—clearly concepts that are corrosive to faith. Thus, it was associated with The Adversary.

One of the earliest explicit disavowals of tritones came from influential Italian composer Guido d’Arezzo, “who intentionally structured the collection of notes in his (then widely-used) hexachordal system to avoid any possibility of a tritone occurring, opting for a B♭ instead of a B♮ to avoid the clash between an F and a B.” However, it’s important to note that neither Guido nor any other composers of his time (roughly 1013 to 1033) referred to tritones as diabolus in musica. As Harvard musicologist and scholar Thomas Forest Kelly explained to me:

I’m not aware of any medieval references to diabolus in musica. The earliest references I know of are from the eighteenth century, and deal with dissonances in polyphonic music, calling various things—the tritone (a f and a b-natural sounding together, for example), the simultaneous or nearby appearance of B-flat and b-natural, and various other kinds of things that might be labeled ‘mi contra fa’ is what’s called “diabolus in music.”

Mi contra fa est diabolus in musica, or “mi against fa is the Devil in music” is a phrase that originated with Joanne Josepho Fux’s 1725 textbook Gradus ad Parnassum. Adam Neely explains that, when employing the hexacord system of Guida d’Arezzo, “Moving from fa, the fourth degree of the commonly used hexachords, to mi in another hexachord might result in a tritone, which is hard to sing.” Neely keenly points out that, in the context of the Gradus ad Parnassum, Fux was not cautioning his reader to avoid the tritone because of any supernatural or religious reasons. Instead Fux’s rationale was pragmatic and was about the technical difficulties of singing to a tritone. It would be later Romantic composers who would arrange compositions around a literal interpretation of the phrase. This brings us to the formal introduction of the tritone into heavy metal. The main riff of the song “Black Sabbath” was inspired by bassist Geezer Butler trying to play part of Gustav Holst’s “The Planets,” specifically, “Mars, the Bringer of War” in which “the melodic line is doubled in the recorder part, using the tritone interval.” Thus, metal was born.

Considering the phrase diabolus in musica didn’t appear until the eighteenth century, it’s simply not possible that the Catholic Church banned the tritone. Like most myths and legends, the story may however have its origins in fact. In either 1323 or 1324, Pope John XXII issued the Docta Sanctorum Patrum, a decretal banning the practice of ars nova, “new art,” a style in Western medieval music that saw composers experimenting with new modes and rhythms. Specifically, the Church sought to defend the monophonic Gregorian chant over the new trend of polyphonic liturgical chants of the ars nova lamenting: 

But certain disciples of a new school, applying themselves to measuring time, invent new notes, preferring them to the old ones. They sing the melodies of the Church with semi-breves and minims, and break these melodies with short notes. They interrupt these melodies with hiccups, soil them with their descant, and even go so far as to add triples and vulgar motets (…) This is why, having taken the advice of our brothers, we order that no one henceforth dare to perpetrate such or similar things, in the said offices, particularly in the canonical hours and the celebration of masses. If anyone acts contrary, he will be punished by the authority of this canon.

It’s important to note that nowhere in the Docta Sanctorum Patrum is the tritone mentioned by name. However, there is one passage in particular that condemns ars nova compositions, saying “Thus they run without resting, they intoxicate the ears instead of soothing them.” I would argue this phrase jives with the nature of tritones as creating in the listener a longing to resolve the tension of the dissonance. Additionally, composers associated with the ars nova movement employed tritones in their compositions; for example, in his Amours me fait desirer, Guillame de Machaut “starts with a surprise, an upward tritone leap, emphasized by the iambic rhythm” (Boogaart 2007).

There’s simply no truth to the claim that the Catholic Church banned the tritone for being diabolus in musica; the tritone was largely (but not entirely) avoided because it was considered aesthetically displeasing. The Church did attempt to ban music that it considered subversive to its doctrine, but it didn’t specifically target the tritone. The phrase diabolus in musica wasn’t even coined by religious authorities; it appeared in a musical textbook as a means of cautioning students that it was technically challenging and ought to be avoided. When I asked for his thoughts on how exactly the myth may have come to be, Magus Gilmore offered:

I think the legends about it arose perhaps from metal musicians who, if they had any training in music theory, remembered the Latin moniker but then leapt to false conclusions about it, and then employed it to have a sort of “instant diabolism” in their own music. Thus, the premise you mentioned is a form of “urban legend,” propagated by folks who really didn’t explore music history to any great extent.

Ultimately, the devil is only in music in the sense that the tritone is a devil of a thing to sing, and, of course, music that does anything but praise God constantly may be considered sinful and wrong. Then again, as Anton LaVey was fond of pointing out, the Devil has always had the best tunes. 

Acknowledgment

Special Thanks to Mark Devoto, Thomas Forest Kelly, and Peter Gilmore for their assistance. Thanks also to Adam Neely, whose YouTube video “The Great Myth of the Medieval Tritone Ban” served as the inspiration for this article.

Reference

Boogaart, L.J.H. 2007. Thought-provoking dissonances. Remarks about Machaut’s compositional licences in relation to his texts. Dutch Journal of Music Theory 12: 273–292.