The Tritone Explained: Music's Most Unstable Interval

Play F and B together on the piano. Something happens immediately — a tense, unstable sound that seems to push toward a resolution it hasn't found yet. That interval is the tritone, and it has fascinated and unsettled musicians for centuries.

The tritone is exactly halfway through the octave: six semitones, three whole tones. That symmetry is the source of both its distinctive sound and its unique properties in harmony. This article explains what the tritone is, why it sounds the way it does, how it drives the most important cadence in tonal music, what jazz musicians discovered about it, and where you can hear it in the music around you.

The intervals chart worksheet covers the full interval system — perfect, major, minor, augmented, and diminished — and is a good companion resource if you want to place the tritone in the broader picture.

What the tritone is

An interval of three whole tones spans six semitones. Starting from C: C to D is a whole tone, D to E is a whole tone, E to F♯ is a whole tone — three tones brings you to F♯. That is an augmented fourth.

But the tritone has two names, depending on how it is spelled.

Augmented fourth (A4): F up to B — four letter names (F, G, A, B), widened by one semitone beyond a perfect fourth. Count the semitones: F–F♯–G–G♯–A–A♯–B = six. Three whole tones, as the name says.

Diminished fifth (d5): B up to F — five letter names (B, C, D, E, F), narrowed by one semitone from a perfect fifth. Count: B–C–C♯–D–D♯–E–F = six semitones. The same distance, different spelling.

The augmented fourth and the diminished fifth are enharmonically equivalent: they span the same number of semitones, so on a keyboard or in equal temperament they sound identical. The difference is in function and spelling. F–B is an augmented fourth; B–F is a diminished fifth. Invert either one and you get the other — which makes sense, because 6 + 6 = 12 (one octave). The tritone is its own inversion.

Augmented fourth F–B (left) and diminished fifth B–F (right): different spellings, the same six semitones. The tritone is symmetrical — it inverts to itself.

Six key facts about the tritone at a glance.

Why the tritone sits at the center of the octave

The twelve-note chromatic scale divides into twelve equal semitones. Six is exactly half of twelve, so the tritone bisects the octave. This is not just a curiosity — it means the tritone is the only interval in equal temperament that is its own inversion, and it explains why the interval sounds so harmonically rootless: neither note feels more important than the other, and neither sounds like a natural "home" for the other to gravitate toward.

Compare that with a perfect fifth (seven semitones). The fifth also sounds stable, and that is precisely because its frequency ratio is so simple (3:2) that one note clearly supports the other. The tritone's frequency ratio in equal temperament is 2 to the power of one half (approximately 1.414:1) — the most complex ratio in the octave, with no neat overtone relationship between the two notes.

That complexity is why theorists and composers have always treated the tritone as a dissonance — an interval that creates tension and demands resolution.

The twelve-semitone octave contains only six tritone pairs, each dividing the octave in half. Jazz tritone substitution exploits this: every tritone pair belongs to two dominant seventh chords a tritone apart.

Where the tritone lives in a major key

In a major key, the tritone appears naturally between two specific scale degrees: scale degree 4 (the subdominant, fa) and scale degree 7 (the leading tone, ti). In C major, those are F and B.

C major: the tritone falls between scale degree 4 (F) and scale degree 7 (B). These two notes frame the dominant chord's internal tension.

Scale degree 7 wants to rise a semitone to the tonic (B → C). Scale degree 4 wants to fall a semitone to the third of the tonic chord (F → E). Those tendencies are built into the scale structure. The tritone is the gap between two notes that have strong, opposite directional pulls — which is exactly what makes it sound tense.

The tritone and the dominant seventh chord

The tritone is the engine of tonal harmony's most powerful move: the dominant-seventh chord resolving to the tonic.

A dominant seventh chord is built on scale degree 5. In C major, that is G7: G–B–D–F. The third of the chord is B; the seventh is F. B and F form a tritone — the same tritone that appears between scale degrees 7 and 4 in C major.

When G7 resolves to C major:

• B resolves up a semitone to C (the root of the tonic chord)
• F resolves down a semitone to E (the third of the tonic chord)

The tritone contracts inward to a major third (B–C and F–E converge by a semitone each). That inward motion — tension releasing to stability — is the acoustic signature of the perfect authentic cadence, and it happens on every V7→I in tonal music.

The tritone B–F in G7 (the third and seventh of the chord) resolves inward: B rises a semitone to C, F falls a semitone to E. The interval contracts from a diminished fifth to a major third.

The dominant seventh worksheet covers the construction and resolution of V7 chords in detail; the cadences worksheet shows this resolution in musical context.

The complementary resolution is the augmented fourth: when F is in the lower voice and B in the upper (F–B), the voices expand outward to a major sixth (F falls to E, B rises to C). Both spellings of the tritone resolve by semitone, but in opposite directions.

The two resolution paths of the tritone. Augmented fourths resolve outward; diminished fifths contract inward. In a standard V7→I cadence (G7→C), the diminished fifth B–F contracts: B goes up to C, F goes down to E.

The tritone in minor keys

Minor keys also contain a tritone, though its location shifts. In natural A minor (the unaltered scale), the tritone falls between scale degrees 2 and 6: B and F. But in harmonic minor — where scale degree 7 is raised by a semitone to create a leading tone — the tritone appears between scale degrees 4 and 7, just as in a major key: D and G♯ in A harmonic minor. This raised seventh is precisely why composers use harmonic minor when writing dominant-seventh chords in minor keys: they need that leading tone to generate the same cadential pull.

The dominant seventh chord in A minor is therefore E7 (using the raised G♯): E–G♯–B–D. The tritone is G♯–D, and it resolves in exactly the same way — G♯ rises a semitone to A (the tonic), D falls a semitone to C♯ (the third of the tonic chord). The pattern holds across all minor keys and is one of the clearest signs that the tritone is not an accidental feature of tonal harmony — it is structural.

"Mi contra fa" — the historical context

The tritone has a long reputation as difficult. Medieval and Renaissance counterpoint treatises warned against it in melodic lines, using the mnemonic mi contra fa est diabolus in musica — "mi against fa is the devil in music." The hexachord system used by medieval theorists labeled certain notes mi and others fa across different overlapping hexachords, and a melodic step or leap that crossed from a mi to a fa from an incompatible hexachord created an interval of a tritone.

This was a practical counterpoint rule, not a Church decree or a ban on the interval. The phrase "diabolus in musica" (devil in music) is used in music-theory writing from roughly the 18th century onward as a colorful label for the tritone's tense character — it was not an official medieval condemnation. Medieval and Renaissance composers used the tritone, particularly in the guise of a diminished fifth between voices; they were careful about it, not forbidden from it. The rule was about melodic voice-leading — leaping a tritone in a single voice — not about the interval appearing in harmony at all.

By the Baroque era, the tritone was fully domesticated as the defining dissonance of the dominant seventh chord. Composers from Monteverdi onward relied on it deliberately to create the tension that makes the cadence satisfying.

The hexachord system in practice. B (mi in the G hexachord) against F (fa in the C hexachord) creates the tritone. The mnemonic mi contra fa est diabolus in musica was a voice-leading caution, not a Church ban — it warned against melodic tritone leaps within a single voice.

Tritone substitution in jazz

Jazz musicians discovered something remarkable about the tritone in the mid-20th century: since a tritone divides the octave exactly in half, there are only six pairs of tritone-related notes, and each pair belongs to two dominant seventh chords a tritone apart.

G7 contains the tritone B–F. What other dominant seventh chord contains those same two notes (or their enharmonic equivalents)? The answer is D♭7: D♭–F–A♭–C♭. The F is the third of D♭7; the C♭ is enharmonically B, the seventh of D♭7. G7 and D♭7 share the same tritone, with the third and seventh swapping roles.

This means D♭7 can substitute for G7 in a cadence to C major. The two chords share the tritone that resolves to C, but D♭7 adds smooth chromatic bass motion (D♭ down a semitone to C) where G7 had a falling fifth.

G7 and D♭7 share the same tritone: B/C♭ and F. Both resolve to C. D♭7 → C major uses semitone bass motion (D♭ → C) instead of the falling fifth of G7 → C.

Tritone substitution gives jazz musicians a smooth-sounding alternative to the standard V7→I cadence, creates chromatic color in bass lines, and is a standard tool in bebop and later jazz harmony.

Tritone substitution compared: G7 → C uses a falling perfect fifth (G → C) in the bass; D♭7 → C uses a descending semitone (D♭ → C). Both arrive at C major and both resolve the shared tritone.

Symmetry: the diminished seventh chord and the whole-tone scale

The tritone is the building block of two symmetrical structures that are central to 19th- and 20th-century harmony.

The diminished seventh chord stacks three minor thirds: for example, B–D–F–A♭. Each pair of notes separated by two steps in the chord (B–F, D–A♭) forms a tritone. Because the chord divides the octave into four equal parts, it has only three distinct transpositions — all other diminished seventh chords are inversions of one of three root forms. This symmetry means the chord can resolve convincingly to any of four different tonic chords, which is why it appears so often as a dramatic pivot in Romantic music.

B diminished seventh (B–D–F–A♭): two stacked tritones, B–F and D–A♭. The chord divides the octave into four equal parts, giving it maximum harmonic ambiguity and the ability to resolve to four different keys.

The whole-tone scale consists entirely of whole tones: C–D–E–F♯–G♯–A♯–(C). Every interval in the scale is a whole tone or a multiple of it, and every pair of notes separated by three scale steps forms a tritone. The scale has only two distinct transpositions (the one above, and the one starting on D♭). Debussy and other Impressionist composers used it to create a floating, directionless effect — precisely because a scale made entirely of tritones has no leading tone, no perfect fifth, and no stable resting point.

The whole-tone scale on C. Every pair of notes three steps apart (C–F♯, D–G♯, E–A♯) forms a tritone. The scale's symmetry gives it a directionless quality; it was used extensively by Debussy.

Famous tritones in music

The tritone appears throughout Western music, from Baroque counterpoint to 1990s film scores. Here are five well-known examples — each verified against the interval structure of the opening or main riff.

Five landmark uses of the tritone in Western music. Each example is verified against the interval structure of the opening or main riff/chord.

Bernstein, "Maria" (West Side Story, 1957): The opening leap — the syllables "Ma-ri-a" — goes from G up to D♭ on the downbeat. That is a diminished fifth of six semitones. It is one of the most discussed tritone openings in the American musical-theater canon, and Bernstein used it deliberately to suggest the aching, unresolved quality of Tony's feeling.

Black Sabbath, "Black Sabbath" (1970): The opening guitar riff is a tritone: G and D♭ oscillating back and forth as a power chord. Tony Iommi chose this deliberately for maximum unsettling effect, and the tritone riff became a defining sound of heavy metal.

The Simpsons theme (1989, Danny Elfman): The ascending brass figure in the main theme includes a tritone leap. The interval gives the theme its cartoonish, slightly off-kilter character.

Jimi Hendrix, "Purple Haze" (1967): The opening riff is built on E and B♭ — a diminished fifth. The main chord used throughout the song is E7♯9 (the "Hendrix chord"), which contains a tritone between its third (G♯) and its dominant seventh (D). The tritone is woven into the chord's color as much as the riff itself.

Wagner, overture to "Tristan und Isolde" (1865): The famous "Tristan chord" (F–B–D♯–G♯) contains a tritone (F–B) between its first two notes, and its deliberately ambiguous resolution — to another dissonance rather than a tonic — made it a touchstone of late-Romantic harmonic instability.

Recognizing the tritone by ear

If you are building your ear-training, the tritone has two reliable reference points among familiar melodies.

The ascending tritone sounds like the opening of "Maria" (G–D♭ on "Ma-ri") or the ascending figure in "The Simpsons" theme. Both open upward with that hollow, tense interval.

The descending tritone sounds like the oscillating power-chord figure at the opening of "Black Sabbath," or like a half-diminished chord collapsing under its own weight.

One useful fact: the tritone is the most distinct interval in the chromatic scale to identify by feel. The unison and octave collapse to the same pitch; the fifth and fourth sound open and stable; the second and seventh bite sharply. The tritone falls squarely in the middle — unstable but not grating, pulling toward resolution without screaming for it. That quality makes it easy to find once you are listening for it.

The hearing intervals worksheet covers all the diatonic intervals with recognition targets; the ear training intervals worksheet gives you active practice, including exercises where you identify the tritone in context.

The tritone is also the easiest interval to recognize by context: in tonal music, whenever you hear a strong dominant chord that "wants" to resolve, the tritone is there inside it, doing the work.

The tritone in practice: writing and reading it

When you write the tritone in a voice-leading context, the standard rules apply:

• Augmented intervals expand: an augmented fourth (F up to B) resolves outward — F falls a semitone to E and B rises a semitone to C — producing a major sixth (E up to C).
• Diminished intervals contract: a diminished fifth (B up to F) resolves inward — B rises a semitone to C and F falls a semitone to E — producing a major third (C up to E).

These are voice-leading conventions, not absolute rules — jazz and 20th-century music break them regularly. But in tonal counterpoint, following the tendency of each tritone note almost always produces a smoother, more natural-sounding resolution.

In jazz and lead-sheet writing, the tritone appears in chord symbols wherever you see a ♭5 (diminished fifth above the root), a ♯11 (augmented fourth above the root), or a dominant seventh chord (which always contains a tritone between its third and seventh). The ♯11 chord (also written as the Lydian dominant) adds an augmented fourth above the root — giving the chord two tritone relationships instead of one, and a distinctive, edgy quality used extensively in film and funk scoring.

A useful practice exercise: take any dominant seventh chord you know and find its tritone. Play just those two notes (the third and seventh of the chord). Then resolve them — the third up a semitone to the root of the tonic, the seventh down a semitone to the third. That movement — two semitones pulling in opposite directions — is the entire engine of the dominant cadence, stripped to its essentials.

The cadences worksheets show the dominant seventh in its standard resolution; identify cadences gives you practice spotting V7→I in real music. Once you can hear the tritone inside a dominant chord, you will start to hear it — and feel its pull — in every cadence you encounter.

Sources

• Tritone — Wikipedia
• Augmented fourth — Wikipedia
• Diminished fifth — Wikipedia
• Tritone substitution — Wikipedia
• Whole tone scale — Wikipedia
• Diminished seventh chord — Wikipedia
• Diabolus in musica — Wikipedia (see "History" section)
• [Richard Bobbitt, Harmonic Technique in the Rock Idiom (1976) — cited in tritone riff analysis]
• [Mark Levine, The Jazz Theory Book (1995), pp. 220–236 — tritone substitution]