A secondary dominant is a chord that acts like a temporary “V chord” pointing at a chord other than the key’s home chord. It borrows the strong pull that a dominant chord has toward the tonic and aims it at a different target inside the progression, adding colour and forward motion without leaving the key for long.
It sounds advanced, but the idea is simple once you see it on a few chords.
First, the regular dominant
In any major key, the chord built on the fifth scale degree (the V chord) wants to resolve to the tonic (the I chord). In C major, G is the V chord and it pulls strongly to C. That pull comes from the leading tone (B) wanting to rise to C, and it is the engine behind most cadences. A dominant 7th chord (G7) makes the pull even stronger, which is covered in our guide to seventh chords.
The secondary dominant idea
Now apply that same pull to a chord that is not the tonic. Take Am, the vi chord in C major. What chord is the “V” of A minor? It is E (or E7). E major is not normally in C major (the diatonic chord on E is Em), so borrowing E7 to lead into Am is a secondary dominant. We call it “five of six,” written V/vi, because it is the V chord of the vi.
So a progression like C – E7 – Am uses E7 as a secondary dominant. The E7 strongly points your ear at Am, making the arrival feel deliberate and rich.
How to build one
The recipe is straightforward:
- Pick the chord you want to lead into (your target).
- Find the note a fifth above that chord’s root.
- Build a major or dominant 7th chord on that note.
For target Dm (the ii chord in C), a fifth above D is A, so A7 is the V/ii. For target G (the V chord), a fifth above G is D, so D7 is the V/V. That D7 contains an F#, a note outside C major, which is the telltale “lift” you hear when a secondary dominant appears.
Common secondary dominants in C major
| Symbol | Chord | Resolves to |
|---|---|---|
| V/ii | A7 | Dm |
| V/iii | B7 | Em |
| V/IV | C7 | F |
| V/V | D7 | G |
| V/vi | E7 | Am |
Why songwriters use them
Secondary dominants add momentum and a touch of sophistication while keeping the song firmly in its key. They are everywhere in pop, jazz, soul and classic rock. A plain C – Am – F – G becomes more interesting as C – E7 – Am – D7 – G, where each new chord pushes toward the next. They are a close cousin of borrowed chords, the difference being that secondary dominants create motion through a temporary V, while borrowed chords change colour by pulling from a parallel key.
Try slotting one into a familiar progression from our common chord progressions list and listen to how it sharpens the pull toward the next chord.
A worked example you can play
Start with the plain progression C – F – G – C in C major and listen to how predictable it feels. Now insert a secondary dominant before the F. The V/IV is C7 (C, E, G, Bb), so play C – C7 – F – G – C. That single Bb note inside the C7 leans the harmony toward F, and the arrival on F suddenly feels intentional and warm. It is a tiny change with an outsized effect, and it is exactly the move that gives so many soul and gospel progressions their pull.
Try the same with V/V. Replace nothing, just lead into the G with a D7: C – F – D7 – G – C. The F# inside D7 gives a clear lift right before the G lands. Layer a vocal on top using chord tones and you have a more sophisticated progression with almost no extra effort.
Where they fit in the bigger picture
Secondary dominants are one of the first “outside the key” tools most writers learn, and they open the door to richer harmony. They pair naturally with seventh chords and with the harmonic logic of the circle of fifths, since every secondary dominant moves to its target by the same strong fifth relationship that drives the circle. Once they feel natural, exploring borrowed chords is the logical next step.
Frequently asked questions
Does a secondary dominant change the key?
No, not permanently. It briefly borrows a chord from outside the key to strengthen the pull toward a target chord, then the song carries on in its original key. It is a tonicisation, not a full key change.
Do secondary dominants have to be 7th chords?
No. A plain major triad works (E instead of E7 before Am), but adding the 7th strengthens the dominant pull and is the more common choice.
How do I spot one by ear?
Listen for a chord that sounds slightly “outside” the key and seems to lead strongly into the next chord. The new sharp or flat note it introduces is your clue that a secondary dominant is at work.
Leave a Reply