Secondary Dominants

You’ll be able to

Explain tonicization and how a secondary dominant borrows a leading tone
Spell secondary dominants such as V/V, V/ii, and V/vi
Resolve a secondary dominant to its temporary tonic

Tonicization and secondary function

A secondary dominant briefly treats a chord other than the tonic as if it were a temporary tonic — a process called tonicization. To tonicize a chord, you precede it with its own dominant: the chord that stands a fifth above it. Unlike a modulation (a lasting change of key), tonicization is fleeting: one chord borrows a chromatic leading tone to spotlight the next chord, then the music returns to the home key. Secondary dominants are notated "V of x," written V/x.

Spelling a secondary dominant

To build V/x, find the root of the target chord x, go up a perfect fifth, and build a major triad (or a dominant seventh) there — adding whatever accidental is needed to create a leading tone into x. In C major, V/V tonicizes G (the V chord): a fifth above G is D, so V/V = D–F♯–A (the F♯ is the raised leading tone to G). Adding the seventh gives V7/V = D–F♯–A–C. Only the target’s leading tone is chromatic; the rest are usually diatonic.

Resolving a secondary dominant

A secondary dominant resolves just like a real dominant, but to its temporary tonic. The borrowed leading tone rises by half step into the target’s root, and any chordal seventh falls by step. So V/V → V, V/ii → ii, V/vi → vi. In C major, V/vi is E–G♯–B (E major); the G♯ leads up to A as the chord resolves to A minor (vi). Because the target is often minor, watch that the secondary dominant itself is major — the chromatic third supplies the leading tone.

Building a secondary dominant

V/x = major triad (or dom7) a perfect fifth above x’s root · V/V in C = D–F♯–A

The chromatic third of V/x is the leading tone of x and resolves up. A chordal seventh resolves down. Compare V/V (D–F♯–A) with diatonic ii (D–F–A): the F♯ is the tell.

Worked example

In C major, spell V7/V and show how it resolves to V.

1.Identify the target: V in C major is G major (the chord to be tonicized).
2.Go up a perfect fifth from G to D and build a dominant seventh: D–F♯–A–C.
3.The F♯ is the chromatic leading tone to G; the C is the chordal seventh.
4.Resolve: F♯ rises to G (the root of V) and C falls to B (the third of V), landing on G–B–D = V.

Answer: V7/V in C major is D–F♯–A–C. Resolving to V (G–B–D), the leading tone F♯ rises to G and the seventh C falls to B.

Checkpoint

In C major, which chord is V/V (the dominant of the dominant)?

Watch out

The giveaway for a secondary dominant is a chromatic (accidental) note that acts as a leading tone into the following chord. Do not mislabel V/V in C as ii just because both are built on D — check the third: F♯ (major, secondary dominant) versus F♮ (minor, diatonic ii).

Checkpoint

In C major, the chord E–G♯–B appears and resolves to A minor. What is this chord’s function?

On the exam

To analyze any chromatic chord, ask: "Does its chromatic tone lead into the root of the next chord by half step?" If yes, it is very likely a secondary dominant of that next chord. Label it V/x (or V7/x), where x is the Roman numeral of the tonicized chord in the home key.

Answer the 2 checkpoints as you read.