Sixth Chord · Theory

Triad Seventh Chord Minor Seventh Chord Inversion Added-Tone Chord

A sixth chord is a triad plus a sixth:

C6 = C–E–G–A (major triad plus a major sixth)

It is often dismissed as unimportant, since a sixth is less conspicuous than a seventh. But it has one very useful property: it is stable, whereas a seventh chord is not.

A coincidence that trips people up

C6 (C–E–G–A) and Am7 (A–C–E–G) contain exactly the same pitches. So are they the same chord?

Viewpoint	Criterion	Verdict
pitch	the keys pressed are the same set	identical
function	which note is the root, and where does it want to go?	different

C6 has C as its root and reads as a stable tonic-function chord; Am7 has A as its root, carries a seventh, and wants to resolve. One set of notes can carry different functions in different contexts — the same logic as enharmonic spelling: same sound, different notation and function.

Two ways to write it

Notation	Meaning	Typical context
C6	triad plus sixth, functionally a C chord	jazz, pop
Am7/C	first inversion of Am7, with C in the bass	traditional harmonic analysis

The same notes; which notation you use depends on what you hear it as. A textbook case of analysis and notation shaping each other.

Why it sounds like relief

Compare two options in the same position:

Cmaj7 (C–E–G–B): the seventh B sits a semitone below the octave, creating suspension (see

major seventh);

C6 (C–E–G–A): the sixth A is two semitones short of the octave, with no suspension.

So the sixth chord is often described as "a major seventh that has resolved". Jazz uses it as a substitute for the major seventh where an ending should feel cleaner and more settled.

Diagram: one set of notes, two roots

Listen: the sixth chord

Hear C6 (settled, landed), then Cmaj7 (suspended). Two options in the same place, with very different closures.

Common misconceptions

"C6 and Am7 are the same chord." Same pitches, different function. The notation you choose follows what you hear.
"A sixth chord is a ninth chord with the ninth added." It contains no seventh; chords with a seventh are seventh and ninth chords.
"A sixth is unstable." A major sixth is consonant, and a sixth chord is stable overall.
"Sixth chords belong to jazz only." Traditional harmony uses the same notes constantly, as an inversion of a seventh chord, under a different notation.

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Listen in the library

Scales, Arpeggios, and CadencesC13:22Scale exercises can sound sixth chords; against seventh chords the difference between a sixth on top and a seventh on top is audibleDetailsSuite bergamasque: III. Clair de luneC14:36Debussy's Clair de lune — sixths and added tones as stable colour, showing its place in the Impressionist vocabularyDetails27. Greensleeves to a Ground with DivisionC10:24Greensleeves to a Ground — in a minor context the sixth often appears as a stable colour toneDetails

All tracks from midicn-lib — inline badge is the license tier (C1 commercial / C2 non-commercial / C3 study only).

Sources

六和弦 = 三和弦 + 六度（根音到六度为大六度或小六度），属和声学通则
六和弦与七和弦的第一转位在音高上重合但功能不同，为通行和声学表述

Used for fact-checking only; all prose is original.

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