A secondary dominant is a dominant 7th chord that points to a chord other than the tonic, such as V/V, the dominant of the dominant. In C major, D7 is the V/V chord, because D7 is the dominant of G major, and it pulls strongly toward G, the V chord of C major.
What are secondary dominants?
A secondary dominant is a dominant 7th chord that points to a chord other than the tonic. In C major, the primary dominant is G7, which points to C major, the tonic. A secondary dominant points somewhere else: D7 points to G major, the V chord, and it is written V/V, the dominant of the dominant. E7 points to Am, the vi chord, and it is written V/vi. A7 points to Dm, the ii chord, and it is written V/ii. Each secondary dominant is a dominant 7th chord built on a note outside the key, and each one creates a V–I cadence in miniature, pulling toward its target chord. Secondary dominants matter because they let a composer create a strong pull toward any chord, not just the tonic, and they add chromatic colour to a progression that would otherwise stay inside the key. A progression that moves C, D7, G sounds more purposeful than a progression that moves C, Dm, G, because the D7 contains an F#, which is not in the C major scale, and the F# pulls toward G, the target chord. That chromatic note is the signature of a secondary dominant, and it is what makes the chord sound so directed. The D7 guitar chord is the V/V chord of C major, and the key of C major shows the chords it points to.
How secondary dominants work
To build a secondary dominant, take the target chord, find its dominant, a perfect 5th above its root, and build a dominant 7th chord on that root. To point to G major, the V chord of C major, find the dominant of G, which is D, a perfect 5th above G, and build a D7 chord, D, F#, A, C. The F# is the chromatic note, because it is not in the C major scale, and it is the note that pulls toward G. To point to Am, the vi chord, find the dominant of A, which is E, and build an E7 chord, E, G#, B, D, where the G# is the chromatic note that pulls toward A. To point to Dm, the ii chord, find the dominant of D, which is A, and build an A7 chord, A, C#, E, G, where the C# pulls toward D. Secondary dominants are written with a slash: V/V means the dominant of the V chord, V/vi means the dominant of the vi chord, and V/ii means the dominant of the ii chord. The chord itself is always a dominant 7th chord, or a major triad, with a major 3rd, because the major 3rd is the chromatic note that creates the pull. In C major the secondary dominants are A7, V/ii, B7, V/iii, C7, V/IV, D7, V/V, and E7, V/vi, and each one points to a different diatonic chord. The E7 guitar chord is the V/vi chord of C major, and the A7 guitar chord is the V/ii chord.
Worked example — V/V in C major. Play the I–V–vi–IV progression in C major, C, G, Am, F, and then replace the V chord, G, with a two-chord movement, D7 to G, so the progression becomes C, D7, G, Am, F. The D7 chord contains an F#, which is not in the C major scale, and the F# pulls toward G, making the arrival at G sound stronger than it did before. The D7 is the V/V chord, the dominant of the dominant, and it creates a V–I cadence in G major inside a song in C major. The D7 guitar chord shows the shape, and the G major guitar chord is the target chord.
How to practise secondary dominants
Practise secondary dominants by adding one to a progression you already know, so your ear learns the pull it creates toward its target chord.
- Play the I–V–vi–IV progression in C major with a D7 chord before the G chord, and listen for the V/V chord pulling toward G.
- Play the same progression with an E7 chord before the Am chord, and listen for the V/vi chord pulling toward Am.
- Find the secondary dominants of the key of G major by building a dominant 7th chord a 5th above each diatonic chord.
- On piano, play a secondary dominant with your right hand and its target chord with your left, and listen for the V–I cadence in miniature.
- Use the chord progression builder to try a secondary dominant in a progression you already know, and hear how it changes the direction.
Common mistakes
- Using a secondary dominant without a target — A secondary dominant points to a specific chord, and it should be followed by that chord. Playing a D7 and then moving somewhere other than G wastes the pull the chord was built to create.
- Forgetting the chromatic note — A secondary dominant needs a major 3rd, which is the chromatic note that creates the pull. Playing a minor 7th chord instead gives you a diatonic chord, not a secondary dominant, and the pull disappears.
- Using too many secondary dominants — One secondary dominant adds direction, but three or four in a row will make the music sound as if it is modulating constantly, and the home key will be lost. Use them sparingly, one at a time, and return to the diatonic chords.
Quick reference
This table lists the secondary dominants of C major, with their notes and their target chords, so you can see that each one is a dominant 7th chord built a perfect 5th above its target. The chromatic note in each row is the major 3rd of the secondary dominant, which is the note that is not in the C major scale and the note that pulls toward the target.
| Secondary dominant | Chord notes | Target chord |
|---|---|---|
| V/ii (A7) | A – C# – E – G | Dm (ii) |
| V/iii (B7) | B – D# – F# – A | Em (iii) |
| V/IV (C7) | C – E – G – A# | F (IV) |
| V/V (D7) | D – F# – A – C | G (V) |
| V/vi (E7) | E – G# – B – D | Am (vi) |
Work through the table by playing each secondary dominant followed by its target chord, and listening for the V–I cadence in miniature. When you can hear the pull in each row, try adding one secondary dominant to a progression you already know, and notice how it changes the direction of the music.
Frequently asked questions
What is a secondary dominant?
A secondary dominant is a dominant 7th chord that points to a chord other than the tonic, such as V/V, the dominant of the dominant. In C major, D7 is the V/V chord, because D7 is the dominant of G major, and it pulls strongly toward G.
How do I build a secondary dominant?
Take the target chord, find its dominant, a perfect 5th above its root, and build a dominant 7th chord on that root. To point to G major, build a D7 chord, D, F#, A, C, where the F# is the chromatic note that pulls toward G.
What does V/V mean?
V/V means the dominant of the V chord: the dominant 7th chord built on the dominant of the dominant. In C major, V/V is D7, because D7 is the dominant of G major, which is the V chord of C major.
Can a secondary dominant point to any chord?
Almost. A secondary dominant can point to any major or minor chord except the tonic and the diminished chord, because those chords do not have a dominant that makes sense. The most common targets are the ii, iii, IV, V and vi chords.
Do secondary dominants change the key?
No. A secondary dominant tonicises its target chord briefly, but the music returns to the home key, and the tonic stays the same. If the music stays in the new key, it has modulated, not tonicised.