Seventh chord
A seventh chord is a triad with a fourth note added a seventh above the root, as in G7 (G–B–D–F) or Cmaj7 (C–E–G–B).
What are the common seventh chords?
Each one is a triad plus a seventh. Built on C:
| Chord | Symbol | Notes | Triad + seventh |
|---|---|---|---|
| Major seventh | Cmaj7 | C–E–G–B | major + major 7th |
| Dominant seventh | C7 | C–E–G–B♭ | major + minor 7th |
| Minor seventh | Cm7 | C–E♭–G–B♭ | minor + minor 7th |
| Half-diminished | Cm7♭5 or Cø7 | C–E♭–G♭–B♭ | diminished + minor 7th |
| Diminished seventh | Cdim7 or C°7 | C–E♭–G♭–B𝄫 | diminished + diminished 7th |
B𝄫 (B double flat) sounds the same as A; it is spelled that way because it is a seventh above C.
Stack one more third on each degree of C major and you get seven seventh chords: Cmaj7, Dm7, Em7, Fmaj7, G7, Am7 and Bm7♭5. Only the chord on the fifth degree, G7, is a dominant seventh.
How do seventh chords sound?
Fuller than a triad, and each type has its own colour. The major seventh sounds soft and airy, with the seventh a semitone below the octave. The minor seventh sounds mellow. The dominant seventh sounds restless: in G7, the notes B and F form a tritone, and resolving to C major (B up to C, F down to E) is the strongest close in tonal music.
That pull drives ii–V7–I, in C major Dm7–G7–Cmaj7: the progression jazz is built on, and one that turns up far beyond jazz.
Does C7 mean C with a B?
No, and this is the most common mistake with chord symbols. A plain 7 means the minor seventh: C7 is C–E–G–B♭, the dominant seventh. The note B appears only when the symbol says maj7: Cmaj7 is C–E–G–B. The two sound very different, so mixing them up is audible straight away.
Try it: The Pull of the Dominant drills progressions with V7 and asks you to hear where the chord is heading.