Pitch & Intervals

Tritone

Pronounced TRY-tone

Definition

A tritone is an interval of six half steps, or three whole steps, such as F–B or C–F♯. Spelled as an augmented fourth or a diminished fifth, it splits the octave exactly in half and sounds tense.

A tritone is the interval of six half steps, or three whole steps, which is where the name comes from (Latin tritonus, "three tones"). F up to B is a tritone: F–G, G–A and A–B are three whole steps. So are C–F♯ and B–F. It measures 600 cents in equal temperament, exactly half an octave.

Augmented fourth or diminished fifth

"Tritone" names only a size, so theory spells it two ways, depending on the letters:

Augmented fourth (A4): four letter names, as in F–B or C–F♯. It is a perfect fourth made a half step wider.
Diminished fifth (d5): five letter names, as in B–F or C–G♭. It is a perfect fifth made a half step narrower.

Three one-bar examples in treble clef of three half notes each: the lower note, the upper note, then both together. F4 and B4; C4 and F sharp 4; C4 and G flat 4. — Three tritones, each shown in one bar: the lower note, the upper note, then both together. F–B and C–F♯ are augmented fourths (four letter names); C–G♭ is a diminished fifth (five letter names), on the same keys as C–F♯.

On the piano, C–F♯ and C–G♭ are the same two keys. The spelling tells you which way the notes want to move, as you will see below.

From C, count six half steps to the black key that is both F♯ and G♭: exactly half of the 12 keys in an octave.

The tritone in the major scale

Each major scale contains exactly one tritone between its own notes: from the 4th degree up to the 7th (F–B in C major), or from the 7th up to the 4th (B–F). That tritone sits inside the dominant seventh chord: G7 is G–B–D–F, and B–F is its tritone. Much of the pull of a dominant chord toward its tonic comes from these two notes.

Resolving a tritone

A tritone is a dissonance that wants to move, and the usual resolution moves both notes by a half step:

A diminished fifth resolves inward, to a third: B–F moves to C–E.
An augmented fourth resolves outward, to a sixth: F–B moves to E–C.

Two treble-clef examples of two half-note chords. Left: B4 and F5, then C5 and E5. Right: F4 and B4, then E4 and C5. — Left: the diminished fifth B–F resolves inward to the third C–E. Right: the augmented fourth F–B resolves outward to the sixth E–C. In both, B rises a half step to C and F falls a half step to E.

It inverts to itself

Turn a tritone upside down and you get another tritone (6 + 6 = 12): an augmented fourth inverts to a diminished fifth. No other interval divides the octave into two equal halves. Jazz musicians exploit this in tritone substitution, replacing a dominant chord with the dominant chord a tritone away, which contains the same tritone.

Its reputation

Singers were long taught to avoid the tritone in melodies, partly because it is awkward to sing in tune, and it picked up the Latin nickname diabolus in musica, "the devil in music". Composers have used its restless sound ever since: a rising tritone opens the song "Maria" from West Side Story, and the interval is common in film music, metal and jazz.

Practice spelling it with Name the intervals: the full toolkit, and compare it with its neighbors in Intervals: the 4th and Intervals: the 5th.

Common questions

How many half steps is a tritone?

Six, or three whole steps. That is exactly half an octave: 600 cents in equal temperament.

Is a tritone an augmented fourth or a diminished fifth?

Either, depending on the spelling. With four letter names (F–B, C–F♯) it is an augmented fourth; with five (B–F, C–G♭) it is a diminished fifth. On the piano they sound the same.

Why is the tritone called the devil's interval?

Its old Latin nickname, diabolus in musica, reflects how unstable it sounds and how hard it is to sing in tune. Stories that the medieval church banned it outright are probably exaggerated: theory books mainly taught singers to avoid it.