Harmony
Secondary dominant
A secondary dominant is a dominant seventh chord that resolves to a chord other than the tonic, such as A7 to Dm or E7 to Am in C major.
What is a secondary dominant?
In a key, the main dominant (G7 in C) leads to the tonic. But every major or minor chord in the key can have its own dominant, built a fifth above it. Played just before that chord, it spotlights it for a moment, as if it were a temporary tonic.
It is written V7/x: V7/V reads "five of five". In C major, D7 is V7/V because it resolves to G. The F# it contains is not in the C major scale, and that outside note creates the pull.
What are the secondary dominants in C major?
| Symbol | Chord | Resolves to | Outside note |
|---|---|---|---|
| V7/ii | A7 | Dm | C# |
| V7/iii | B7 | Em | D# |
| V7/IV | C7 | F | B♭ |
| V7/V | D7 | G | F# |
| V7/vi | E7 | Am | G# |
The vii° chord (Bdim) has no secondary dominant: a diminished chord is too unstable to act as a temporary tonic. The outside note is always a leading tone or a seventh: C# rises to D, G# rises to A, B♭ falls to A.
How to play secondary dominants on guitar
Start with open shapes in C major:
- C A7 Dm G7 C: x32010, x02020, xx0231, 320001, x32010. The C# of A7 (2nd fret, 2nd string) rises to the D of Dm (3rd fret, same string).
- C E7 Am: E7 (020100) then Am (x02210). The G# at the 1st fret of the 3rd string rises to A at the 2nd fret.
- C C7 F: C7 (x32310) adds B♭ at the 3rd fret of the 3rd string, which slides down to A at the 2nd fret in F.
For a richer sound, chain them around the circle of fifths: E7 A7 D7 G7 C. Each chord is the dominant of the next one, a sound typical of ragtime and swing.
How to use them in songwriting and soloing
The simplest method: before any diatonic chord, insert the dominant seventh built a fifth above it. C Am F G becomes C E7 Am F G. It is one of the basic tools of reharmonization.
You can also put its own ii in front of it: Em7 A7 Dm7 is a secondary ii-V into Dm. When soloing, target the outside note on the secondary chord (G# over E7, C# over A7), then resolve it by a half step. If the secondary dominant lasts several bars and the song stays in the new key, you are dealing with a modulation. The chord substitutions module lists the secondary dominants of each chord with playable voicings.
Key takeaways
- A secondary dominant is the V7 of a chord other than the tonic: V7/V, V7/vi...
- In C: A7, B7, C7, D7 and E7 target Dm, Em, F, G and Am.
- The outside note is a leading tone that resolves by a half step.
- Chained around the circle of fifths, they give E7 A7 D7 G7 C.
Frequently asked questions
Does a secondary dominant have to be a seventh chord?
No. A major triad is enough: D to G in C major is already V/V. The seventh strengthens the pull through the tritone, which is why it is usually added.
What is the difference between a secondary dominant and a modulation?
A secondary dominant highlights a chord for a beat or two, then the original key carries on. A modulation establishes a new tonic for a while, with its own cadences.
Why does E7 sound so good in C major?
Because it is V7/vi: it leads to Am, the relative minor. Its G# is a leading tone to A and gives a dramatic colour heard in countless pop, bossa nova and singer-songwriter tunes.
Related terms
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