Chord Symbols · Jazz Wiki

A chord symbol is a compressed instruction, not a full score. It tells a player the root, the quality, any extensions or alterations, and sometimes a bass note — and then gets out of the way. Everything else — which octave, which inversion, how many notes, what rhythm, whether it’s arpeggiated or slammed as a block — is left to the musician.

Why a Symbol Isn’t a Full Score

This is the whole premise of jazz as a realized music rather than a fully notated one: the lead sheet gives you the skeleton, and comping is the act of clothing that skeleton in real time. Two pianists reading the exact same G7 will voice it differently, and both are correct. That’s not sloppiness; it’s the point.

Anatomy of a Symbol

Take G7(♭9♯5) apart and the logic is plain: the root is G, “7” says dominant quality, and the parenthesized part lists alterations — the 9th flatted, the 5th sharped. A slash adds a bass note that isn’t necessarily the root, giving a compact way to write an inversion (see Slash Chords).

G7(♭9♯5) → root G, dominant 7th quality, alterations ♭9 and ♯5
C/E → C major triad over an E bass note, a first-inversion sound written compactly

Quality Families and Their Spellings

The plain number 7 always means dominant — C7 spells C E G B♭, never B natural. This trips up nearly every beginner: C7 and Cmaj7 are not the same chord, and mixing them up is the single most common misreading in the seventh chord vocabulary. Each quality family carries its own spelling and its own shorthand:

Quality family	Symbol	Common aliases	Notes spelled
Dominant Seventh Chord	C7	—	C E G B♭
Major Seventh Chord	Cmaj7	CM7, CΔ7	C E G B
Minor Seventh Chord	Cm7	C−7, Cmin7	C E♭ G B♭
Half-Diminished Chord	Cø7	Cm7♭5	minor triad with a flat 5 and a minor 7th; Bø7 = B D F A
Diminished Seventh Chord	C°7	Cdim7	stacked minor thirds; B°7 = B D F A♭ — genuinely different from Bø7 (A versus A♭, a minor 7th versus a diminished 7th above the root, worth ear-training on its own)
Suspended Chords	Csus4	—	the 3rd replaced by a 4th
Sixth Chords	C6 / Cm6	—	the 6th degree added instead of a 7th, common in older repertoire and as a resolution color

Written out, the difference between C7 and Cmaj7 is a single accidental:

The other seventh-chord qualities each move one or two of those notes:

Extensions, Add Chords, and House-Style Quirks

A number bigger than 7 implies the 7th and everything below it is already there. This shorthand is part of the broader system of Chord Extensions and Chord Alterations, and the conventions around parentheses, sharps, and flats fall under Jazz Notation Conventions:

Cmaj9 = C E G B D (major 7th plus 9th)
C13, in practice, = C E G B♭ D A (dominant 7th plus 9, 11, 13 — the 11th is usually dropped since it clashes with the major 3rd)
Cmaj9 (7th present) versus “Cadd9” (9th added, no 7th at all) — a small notational detail that changes the harmony completely

House styles genuinely disagree on top of all this: Δ sometimes means “just a major triad” in older or European charts, though in American jazz practice it almost always means major 7th, and “−” versus “m” for minor is purely a house-style choice with no musical difference. This is why the culture of the Real Book matters so much: it standardized (imperfectly) a shared shorthand that lets a rhythm section that has never rehearsed together sit down and play a tune correctly, voicing it however they like. The symbol guarantees the notes belong to the chord; it says nothing about how they get arranged.

♫ Listen

Cannonball Adderley — “Autumn Leaves” (Somethin’ Else, Blue Note, 1958): Hank Jones’s full, harmonically dense comping behind Miles Davis’s spare melodic lines — one chart of chord symbols, two completely different realizations happening simultaneously. Listen through the intro and first melody chorus.
Bill Evans Trio — “Autumn Leaves” (Portrait in Jazz, 1960): the same tune’s chord symbols realized as rootless, close-voiced piano chords. Put it right next to the Adderley/Jones version above and hear how differently “the same changes” can sound.
Miles Davis — “So What” (Kind of Blue, 1959): the famous piano-and-bass call-and-response essentially plays a single Dm7 symbol as a stacked-fourths voicing — a striking example of how much a symbol leaves open.