Jazz harmony essentials — the engine room
Six concepts cover ninety percent of what happens in a standard. Take them one at a time and the chord-symbol wall comes down.
1. The ii–V–I — the atom of jazz
In C: Dm7 → G7 → Cmaj7. The roots fall in fifths; inside the chords, the 7th of each resolves down a half-step to the 3rd of the next (C→B, F→E). That half-step fall is the "melt" you hear. Major-key version above; the minor-key version is Dm7♭5 → G7(♭9) → Cm — same engine, darker fuel. Standards are substantially chains of ii–Vs visiting different keys; learn to spot them as units and a sheet of changes becomes three or four sentences instead of thirty symbols.
2. Turnarounds
The jazz turnaround is I–VI–ii–V (C–A7–Dm7–G7): two beats each, landing you back at the top. Every variant is a substitution on that frame: iii–VI–ii–V (Em7 for C), or the half-step "Lady Bird" version I–♭III7–♭VImaj7–♭II7. Loop one for ten minutes and you'll recognise it in a hundred tunes.
3. Secondary dominants
Any chord can be preceded by its own V7 — that's the whole trick. The A7 in a C-major turnaround is "V of ii": it doesn't belong to C, it belongs to the Dm it's aiming at. The chord builder's secondary-dominants row is exactly this device; jazz simply uses it relentlessly.
4. Tritone substitution
Every dominant 7th shares its two crucial notes (the 3rd and 7th — the tritone) with the dominant a flattened fifth away: G7 and D♭7 both contain B and F. So either can resolve to C — and substituting D♭7 for G7 turns the bassline ii–V–I into a chromatic slide: D–D♭–C. That slinky half-step bass is one of the most recognisable sounds in jazz, and it's one substitution rule, applied everywhere.
5. The passing diminished
Between IV and the I/5 sits the ♯IV diminished (in B♭ blues: E♭7 → E°7 → B♭/F); between I and ii sits ♯I°7. Diminished chords are harmonic stairs — every note wants to step up. You met one in bar 6 of the jazz blues; gospel and Stevie Wonder run on the same stairs.
6. Shell voicings — how guitarists actually play this
Forget six-string grips. Jazz guitar comping is built on shells: root + 3rd + 7th, or just 3rd + 7th once a bassist owns the root. The 3rd and 7th define the chord's quality and contain all the voice-leading motion — and they sit under two fingers. Learn shells for ii–V–I in two positions and you can comp through most of the repertoire; add 9ths and 13ths on top later, as melody, not as furniture.
| Device | Sound | Hear it in |
|---|---|---|
| ii–V–I | Dm7 G7 Cmaj7 | Autumn Leaves (built from almost nothing else) |
| Turnaround | C A7 Dm7 G7 | I Got Rhythm A section, Blue Moon |
| Tritone sub | Dm7 D♭7 Cmaj7 | The Girl from Ipanema (final cadence), Satin Doll's tail |
| Passing dim. | E♭ E°7 B♭/F | Bar 6 of any jazz blues; This Masquerade |
| Minor ii–V | Dm7♭5 G7♭9 Cm | Autumn Leaves' second phrase, Blue Bossa |