The forbidden chord

Is it really a chord?

Strictly it is an interval: two notes, not the three or more of a chord. The name “forbidden chord” stuck because guitarists play it as a shape, and because it sits inside chords you already know. In E7 the notes G♯ and D are a tritone apart; a diminished seventh chord holds two of them.

Was it really banned?

No law of the church ever banned it, and the stories of singers punished for it are legends. Singers in the Middle Ages did steer around F against B, because of the system of six-note scales they learned from (the clash was called mi contra fa). The Latin nickname diabolus in musica is not found in medieval writing: the first known uses are from the early 1700s, by theorists such as Andreas Werckmeister and Johann Joseph Fux.

Why does it sound so tense?

The tritone splits the octave exactly in half: E up to B♭ is the same distance as B♭ up to E, so neither note sounds like home. Ears want it to move, and it usually does: in E7 going to A, the G♯ rises to A and the D falls to C♯. That pull is what makes a seventh chord lead so strongly to the next one.

Where you have heard it

The opening riff of Black Sabbath’s song “Black Sabbath” is built on it, and so is the start of Jimi Hendrix’s “Purple Haze”, whose Hendrix chord also holds one. It runs through Leonard Bernstein’s music for West Side Story.

Other things people call forbidden

• A diminished chord. Some lessons called “the forbidden chord” teach a diminished chord, which is built on a tritone.
• The C♯ power chord. A running online joke says C♯5 was banned. There was no ban, and C♯5 (C♯ and G♯) is a fifth, not a tritone.
• The forbidden riff. The “No Stairway to Heaven” sign in a guitar shop in Wayne’s World (1992): a riff shop staff were tired of hearing, not a chord.

Questions

What is the forbidden chord?

The tritone: two notes six half steps apart, such as E and B♭, also called the devil’s interval. It is an interval rather than a chord, but it sits inside seventh and diminished chords.

How do I play the forbidden chord on guitar?

Play the open low E string with the A string at the first fret (B♭): 01xxxx. Or put a flat five on a power chord: 34xxxx, G and D♭.

Was the tritone banned by the church?

No. There is no record of any ban. Medieval singers avoided it, and the nickname diabolus in musica only appears in writing from the early 1700s.

Why is it called the devil’s interval?

The Latin name diabolus in musica, the devil in music, was given to it by music theorists in the 1700s, for the hard clash it makes when it is not resolved.

Is the C sharp power chord banned?

No. It is an online joke. C♯5 is C♯ and G♯, a perfect fifth, and nothing has ever banned it.

Sources

• Tritone (Wikipedia)
• The devil’s chord: the eerie history of diabolus in musica (Fender)
• What is the forbidden chord? (Breakthrough Guitar)

More chord stories: The saddest chord, The four chord song, The Picardy third, The most beautiful chord, The happiest chord, The Mario cadence, and famous chords such as the Tristan chord and the Hendrix chord. Also: the guitar chord library, the chord finder and the chords in every key.