The problem it solves
Once triads say all you want, you reach for more colour, more tension and the chromatic slip of jazz. You need to know how chords expand with sevenths and extensions and how dominants are reharmonized.
Detailed theory
Key idea
Seventh chords (not triads) are the default; the ii-V-I is the central progression and the extensions 9, 11 and 13 add colour.
The tritone substitution swaps a dominant for the dominant a tritone away because they share the same tritone, giving a bass that slips down a semitone.
Understand it
Jazz harmony does not invent a new system: it extends the tonal one. The first change is that the default chords have four notes — sevenths — instead of triads. Maj7, m7 and 7 (dominant) replace major and minor triads as the base sonority.
The central progression is the ii-V-I (for example Dm7-G7-Cmaj7): the ii prepares, the V creates dominant tension and the I resolves. This pattern is the axis around which most of the repertoire turns.
On top of the chords you add extensions or tensions — the ninth (9), the eleventh (11) and the thirteenth (13) — that enrich the colour without changing the chord’s function. They are the notes that give the characteristic lush sound.
Dominants can be reharmonized. The most famous is the tritone substitution: you swap a dominant for the dominant a tritone away. It works because both share the same guide tritone: G7 and Db7 both contain the tritone B-F (in Db7, the F and the Cb/B). Replacing G7 with Db7, the bass slips chromatically down a semitone to the tonic (Db→C).
Think of it as making the same harmonic journey but taking colourful side-streets (substitutions, extensions) instead of the main avenue: you reach the same place, but the route sounds richer. Another common move is the backdoor (bVII7→I), which resolves to the tonic from an unexpected dominant.
Chord progression
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The tritone substitution: Db7 replaces G7 (they share the tritone B-F) and the bass slips chromatically Db→C to the tonic.
How to recognise it
How it's written
Read the four-note chord symbols: maj7, m7 and 7 give the chord quality, and the added numbers (9, 11, 13, or alterations like b9, #11) are the extensions. Faced with a dominant that resolves by falling a semitone in the bass (for example Db7→Cmaj7), suspect a tritone substitution.
How it feels
Listen to a ii-V-I and then swap the V7 for its tritone (Db7 instead of G7): you will notice how the bass slips chromatically toward the tonic and how the colour turns more tense and elegant, even though it resolves to the same place.
Common mistake
Playing triads where jazz asks for sevenths: the base sonority of jazz is the four-note chord, not the triad.
Thinking the tritone substitution is arbitrary: it only works because the two dominants share the same guide tritone (B-F).
Try it
Play the ii-V-I Dm7-G7-Cmaj7 and hear the base sonority of jazz with seventh chords.
Swap the G7 for Db7 (Dm7-Db7-Cmaj7) and notice the bass slipping Db→C, a semitone down.
On the instrument
Chord progression
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The jazz ii-V-I in C major with seventh chords: Dm7-G7-Cmaj7. The central progression of the language.
Where it's used
- Playing jazz standards
- Recognising and comping the ii-V-I with seventh chords, the central progression of the repertoire.
- Reharmonizing dominants
- Applying the tritone substitution (swapping V7 for its tritone) for a more colourful chromatic bass.
- Adding colour with extensions
- Enriching chords with tensions (9, 11, 13) without changing their harmonic function.
Examples
Example with rhythm
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The central jazz ii-V-I as a chorale in C major: Dm7-G7-Cmaj7, each chord a four-note column with seventh chords (not triads). The ii prepares, the V creates dominant tension and the I resolves. This is the progression most of the repertoire turns on.
Example with rhythm
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The same ii-V-I with the tritone substitution: Dm7-Db7-Cmaj7. Db7 replaces G7 because both share the same guide tritone (B-F: in Db7, the F and the Cb/B). The bass, highlighted, slips chromatically D→Db→C, a semitone down, instead of the G→C leap.
Generate a new example
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Generate fresh jazz ii-V-I in any key (Dm7-G7-Cmaj7 transposed at random). Press for a new one and hear the central jazz progression built on seventh chords.
Exercises
Recognise jazz seventh chords
Advanced progressions, dictation and analysis exercises.
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Mini test
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0/7 answeredQuestion 1/7
What is the base sonority of jazz harmony?