Secondary dominants and approach chords: the complete guide

A secondary dominant is a "borrowed" chord that creates momentary pull toward another chord in the key — as if, for a few bars, the music gained a new center of gravity. Instead of using only the key's natural chords, you set up the arrival of one of them with its very own dominant, and the ear starts hearing that destination as especially important.

What a secondary dominant is

Every major key has a main dominant: the chord built on the fifth degree, with a seventh. In C major, that is G7, which points strongly toward C. The pull comes from two inner notes: the leading tone (B, which wants to rise to C) and the chord's seventh (F, which wants to fall to E). A secondary dominant applies exactly the same mechanism to another chord in the key: any degree can, for a moment, get a dominant all its own. And along with it comes a note from outside the scale — the so-called chromatic leading tone, which is the spice of the technique.

How to build one: the V7/x formula

The notation V7/x reads "dominant of x". In practice the recipe is simple: pick the chord you want to set up, go up a perfect fifth from its root (or down a fourth — same note) and build a major chord with a seventh there. Want to set up Dm in C major? A fifth above D is A: the result is A7, resolving to Dm.

The five secondary dominants of a major key

• V7/ii — in C major, A7 resolving to Dm: the C sharp, a note foreign to the scale, rises a half step and "delivers" the D.
• V7/iii — B7 resolving to Em: it brings two chromatic notes (D sharp and F sharp), which makes it the most colorful of the five.
• V7/IV — C7 resolving to F: the first-degree chord itself gains a minor seventh (B flat) and starts pointing toward the fourth degree.
• V7/V — D7 resolving to G or G7: the F sharp sets up the main dominant; one of the most frequent in any style.
• V7/vi — E7 resolving to Am: the G sharp leads to the relative minor; a constant presence in popular music.

What about the seventh degree? It normally doesn't get a dominant of its own: the chord built there is diminished — that is, unstable by nature — and so it never convinces the ear as a point of arrival. There is no stable target to tonicize.

Tonicizing is not modulating

When a secondary dominant resolves and the music keeps orbiting the original key, we say a tonicization happened: a passing highlight, a kind of "zoom" onto one chord. Modulation is something else: the music actually moves to a new key and stays there. The test is what comes next — if, after the resolution, everything goes back to orbiting the original center, it was only a tonicization.

Hear the difference in a progression

Play or imagine this sequence in C major: C – E7 – Am – A7 – Dm – D7 – G7 – C. Each secondary dominant introduces a chromatic note that pushes into the next chord: the G sharp in E7 rises to the A of Am; the C sharp in A7 delivers the D of Dm; the F sharp in D7 sets up the G of G7. Now compare with the purely diatonic version, C – Em – Am – Dm – G7 – C: the harmony is still correct, but it loses much of its direction and drive. That feeling of an "arrow pointing forward" is what the technique adds.

Approach chords from the same family

Every secondary dominant welcomes company: you can precede it with its own "second degree", forming what is called a related ii–V. Instead of going straight from C to A7 and Dm, try C – Em7(b5) – A7 – Dm. When the target is a minor chord, that second degree usually comes with a diminished fifth, like Em7(b5); when the target is major, a minor seventh chord works nicely, as in Am7 – D7 – G.

Two other approaches live in the same neighborhood. The tritone substitution swaps the dominant for another seventh chord located three whole steps away — Db7 in place of G7 before C, for example — keeping the two notes that generate the tension and gaining a bass that descends by half step into the destination. The passing diminished chord, in turn, links two neighboring chords with a chromatic diminished chord: an in-between step that shares notes with the corresponding dominant and plays a similar role in less space.

Are secondary dominants only for sophisticated music?

No. They show up in simple songs across virtually every popular style — often without the songwriter ever thinking of the technical name. Whenever a major seventh-type chord appears from outside the key and resolves down a fifth, the technique is at work.

How do I spot a secondary dominant in a chord chart?

Look for a seventh chord that doesn't belong to the key and watch where it goes: if the next chord sits a fifth below (or a fourth above) its root, it's almost certainly a V7/x. In C major, an A7 followed by Dm is the classic example.

On your instrument

Next level, no mystery: in the Chord & Fret app you hear, see and play every variation — on your phone, via the stores.

References

Content reviewed against the standard harmony literature — verified bibliography below.

• Carlos Almada — Harmonia Funcional (Editora da Unicamp, 2009; 2ª ed. 2012)
• Bohumil Med — Teoria da Música (Musimed)
• Stefan Kostka; Dorothy Payne; Byron Almén — Tonal Harmony (McGraw-Hill)
• Edward Aldwell; Carl Schachter; Allen Cadwallader — Harmony and Voice Leading (Cengage)
• Jerry Coker — Elements of the Jazz Language for the Developing Improvisor (Alfred, 1991)
• Open Music Theory

Updated July 9, 2026