Secondary dominants
Dominant chords that point to a degree of the key other than the tonic, adding chromatic colour without changing key.
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Dominant chords that point to a degree of the key other than the tonic, adding chromatic colour without changing key.
Advanced
In C major, G7 is the dominant of the tonic. But any major or minor chord in the key can have its own dominant: a dominant seventh chord a perfect fifth above it. These are secondary dominants, written V/x ("five of…"): A7 is V/ii because it resolves to Dm.
First, a progression with diatonic chords only. Then the same one with a secondary dominant before Dm:
I – vi – ii – V7 – I I – V7/ii – ii – V7 – IThe key change is a single note: Am has C, and A7 has C♯, which acts as the leading tone of D:
The secondary dominants of C major:
| Symbol | Chord | Resolves to | Chromatic note |
|---|---|---|---|
| V7/ii | A7 | Dm | C♯ |
| V7/iii | B7 | Em | D♯ (and F♯) |
| V7/IV | C7 | F | B♭ |
| V7/V | D7 | G | F♯ |
| V7/vi | E7 | Am | G♯ |
There's no V/vii°, because a diminished chord can't act as a temporary tonic.
String 6, Open: E2 · 1 · Root
Take a diatonic progression and, before any chord (except vii°), insert the dominant a fifth above it. Start with V7/V, the most common:
I – V7/V – V7 – IThen try a chain of dominants, each resolving into the next:
Chained dominantsWhen improvising, the chromatic note is the key: over A7 in C major, swap C for C♯. A simple option is the key's scale with that one note altered.
You can precede a secondary dominant with its own ii, like a miniature ii–V: Em7 – A7 – Dm7. If the target is minor, the ii is usually half-diminished: Bm7♭5 – E7 – Am. It's the most frequent device in jazz standards, as Levine explains.
Ear & improvisationTarget tonesImprovise over a backing track aiming at a specific tone of each chord.Kostka and Payne, and Aldwell and Schachter, distinguish tonicization (a chord is briefly treated as a tonic) from modulation (the key really changes, confirmed by a cadence in the new key). The boundary is gradual: it depends on duration and on whether a cadence appears.
Besides V7, there are secondary leading-tone chords, vii°7/x: C♯dim7 before Dm does the same job as A7 and contains its leading tone and seventh. In jazz, any secondary dominant can in turn be replaced by its tritone substitute.