BazzLow
ENIT
Module 10 · Lesson 4

The dominant seventh

Understand why the V7 chord pulls so strongly to I.

Before this lesson: 10.3 Diatonic seventh chords · 4.4 Augmented, diminished and the tritone

One chord pulls to the tonic harder than any other. It is built from the notes of the key, and it contains the tension the key needs to feel resolved.

V7

The dominant seventh (V7) is the seventh chord on the 5th degree. In C: G7 = G B D F. It contains a tritone between its 3rd and 7th: B–F (lesson 4.4). The tritone is unstable, and it resolves by half steps:

  • the 3rd of V7 (B, the leading tone) rises to the root of I (C);
  • the 7th of V7 (F) falls to the 3rd of I (E).

At the same time the root moves down a 5th (G → C), the strongest root movement (lesson 8.4). Bass and tritone together make V7 → I the strongest resolution in tonal music.

RootThirdFifthSeventh2nd, 4th, 6th
Bass neck, frets 0–12G7 resolving to C: B (fret 2 on the A string) rises to C (fret 3); F (fret 3 on the D string) falls to E (fret 2); the root G (fret 3 on the E string) moves to C (fret 3 on the A string).DAE123456GBDFCE
G7 resolving to C: B (fret 2 on the A string) rises to C (fret 3); F (fret 3 on the D string) falls to E (fret 2); the root G (fret 3 on the E string) moves to C (fret 3 on the A string).

Dominant by sound

Any chord with the formula 1 3 5 ♭7 is called a “dominant 7th” by its sound, even when it is not on degree 5. In the blues, I7, IV7 and V7 are all dominant-7th chords (Module 12). A 7-chord on another degree often acts as the V of the chord that follows (a secondary dominant, Module 14).

Where does V7 come from? Its notes are all in the major key. Seen from its own root, the scale it uses is the Mixolydian mode, a major scale with ♭7 (Module 13). Goodman calls this the “dominant scale”.

For the bass

On a V7 the root is the main note, and the ♭7 is a strong colour or passing note: it falls naturally to the 3rd of the next chord.

The dominant chain

On the circle of fifths, each key is the V of its counter-clockwise neighbour. E7 → A7 → D7 → G7 → C is a dominant chain: dominants resolving down in 5ths.

Try it

Play G (fret 3 on the E string) → C (fret 3 on the A string) roots. Then play the arpeggio of G7 ending on F, followed by E (the 3rd of C). Hear F “fall” into E.

New terms