Seventh chords

Also called 7th chords

A seventh chord is a triad plus the note a seventh above its root. The five common kinds are major seventh, dominant seventh, minor seventh, half-diminished and diminished seventh.

How is a seventh chord built?

Stack three thirds on the root and you have four notes: root, third, fifth, seventh. A triad stops at the fifth; a seventh chord goes one third further. What tells the kinds apart is which of the thirds are major and which are minor. Those choices decide how far the seventh sits above the root: 11 half steps (a major seventh), 10 (a minor seventh) or 9 (a diminished seventh).

The five seventh chords on C, each with its chord symbol: Cmaj7, C7, Cm7, Cm7♭5 and Cdim7.
ChordSymbol on CBuilt asNotes
Major seventhCmaj7major triad + major 7thC–E–G–B
Dominant seventhC7major triad + minor 7thC–E–G–B♭
Minor seventhCm7minor triad + minor 7thC–E♭–G–B♭
Half-diminished seventhCm7♭5diminished triad + minor 7thC–E♭–G♭–B♭
Diminished seventhCdim7diminished triad + diminished 7thC–E♭–G♭–B𝄫

The names are less odd than they look. “Major seventh” and “minor seventh” name the seventh itself, measured up from the root. “Dominant seventh” is a major triad with a minor seventh, the chord on the fifth degree of a major key. “Half-diminished” is a diminished triad with a minor seventh; “fully diminished” puts a diminished seventh on the same triad, so every third is a minor third.

Which seventh chords belong to a major key?

Build a seventh chord on every note of a major scale using only notes of the scale, and the kinds come out in a fixed order: major seventh, minor seventh, minor seventh, major seventh, dominant seventh, minor seventh, half-diminished. Only the chord on the fifth degree is a dominant seventh, which is why it is the one that sounds like a signpost.

DegreeNumeralSymbol in CKind
1Imaj7Cmaj7major seventh
2ii7Dm7minor seventh
3iii7Em7minor seventh
4IVmaj7Fmaj7major seventh
5V7G7dominant seventh
6vi7Am7minor seventh
7viiø7Bm7♭5half-diminished

Common questions

What is a half-diminished chord?

A diminished triad with a minor seventh on top, such as B–D–F–A. It is written ø or m7♭5, and in a major key it sits on the seventh degree.

What is the difference between Cmaj7 and C7?

Both add a seventh to a C major triad, but Cmaj7 adds B and sounds smooth, while C7 adds B♭ and sounds restless. Only the one marked 7 is a dominant-seventh chord.

How many seventh chords are there in a major key?

Seven, one per degree, but only four kinds: major seventh on I and IV, minor seventh on ii, iii and vi, dominant seventh on V and half-diminished on vii.