The Tritone · Jazz Wiki

The tritone splits the octave exactly in half—six semitones up, six down, no favoritism. That perfect symmetry is what makes it the least stable interval in Western music: your ear can’t decide which way it wants to fall, so it pulls hard toward resolution. Nearly everything that makes jazz harmony feel like it’s moving—dominant resolution, tritone substitution, the whole engine of the ii-V-I—traces back to this one unstable interval.

What it is, and why it has two names

A tritone spans six half steps—three whole tones, hence the name. Depending on how you spell it, it’s either an augmented 4th or a diminished 5th, and in equal temperament these are literally the same pitch distance, just named for different musical purposes.

Augmented 4th: F–B (in C major)
Diminished 5th: B–F (in C major)

Classical theory keeps these names separate because they resolve differently: an augmented 4th tends to pull outward to a 6th, a diminished 5th pulls inward to a 3rd. Jazz players mostly don’t bother with the distinction—they just call it “the tritone” or “the b5” and think about where it wants to go.

The same six semitones, spelled two ways:

The engine inside every dominant chord

Take any Dominant Seventh Chord and look at its 3rd and 7th—those two notes are always a tritone apart. That tritone is the reason a dominant chord sounds unfinished, restless, like it has to go somewhere.

G7 = G–B–D–F
Tritone inside: B (3rd) and F (7th)
Resolving to Cmaj7: B–F → C–E

Notice the voice leading: B is the leading tone and climbs a half step to C, while F drops a half step to E, the third of the tonic chord. Those two half-step pulls, converging from opposite directions, are what “resolution” physically sounds like—the tension of dissonance collapsing into consonance. This is the whole story of Tension and Release compressed into two notes.

Symmetry: the trick that makes substitution possible

Because the tritone is its own inversion—invert it and you get another tritone—two dominant chords a tritone apart end up sharing the exact same pair of notes for their 3rd and 7th.

G7’s tritone: B–F
D♭7’s tritone: F–C♭ (= F–B, same pitches, respelled)

Since B–F is doing the same tension-and-release work in both chords, G7 and D♭7 are functionally interchangeable—this is Tritone Substitution, the single most common reharmonization trick in jazz.

B–F cuts the chromatic clock exactly in half — six semitones each way — so the interval is its own inversion, and G7 and D♭7 share this same diameter as their 3rd and 7th

Original: Dm7 – G7 – Cmaj7
Substituted: Dm7 – D♭7 – Cmaj7

The guide tones barely move, but the bass now walks down chromatically (D→D♭→C) instead of leaping a fourth, which is why the substitution sounds so smooth even though the chord symbol looks like a shock on paper.

Where the tritone lives outside of V7

The tritone isn’t only a dominant-chord phenomenon. It’s the defining color of Locrian Mode, where the root and the 5th degree are a tritone apart instead of a perfect 5th—that’s exactly what makes Locrian sound so unresolved and hard to use as a “home” sound. It also sits inside The Blues Scale as the famous “blue note” b5, but there it isn’t demanding resolution at all—it’s just a color, sustained and enjoyed rather than resolved, which is a genuinely different use of the same interval.

As for the old story that the medieval Church banned the tritone as diabolus in musica, the devil in music—that’s overstated. Medieval and Renaissance composers avoided it because it was hard to tune and sounded acoustically rough in their systems, not because of demonology; the “diabolus” label itself only shows up in theory texts from the 18th century, long after the fact. The real medieval objection was practical, not superstitious.

♫ Listen

Dizzy Gillespie — “A Night in Tunisia” (1946): the flatted fifth is baked into the melody itself—listen for the bright, piercing bite of the augmented 4th in the trumpet line, and notice how the tension drives rather than jars against the rhythm.
Charlie Parker — “Anthropology” (1946): Parker outlines the b5 constantly in his bebop phrasing, especially through the bridge—listen for how naturally the tritone slots into fast eighth-note lines as a passing color, not just a resolution tone.
Thelonious Monk — “'Round Midnight” (Thelonious Himself, 1957): built on tritone substitutions and angular, unresolved-feeling voicings—listen for how Monk lets the tension sit rather than snapping it shut, giving the tune its eerie, suspended quality.