# Secondary dominants

*Module 14 · Lesson 3: Beyond the key · BazzLow*

> Recognise secondary dominants and their effect on the bass line.

Before this lesson: [10.4 The dominant seventh](https://bazzlow.com/en/seventh-chords/dominant-seventh/) · [8.4 Chord function](https://bazzlow.com/en/harmony-in-a-key/chord-function/)

A 7-chord that does not belong to the key is usually a dominant in disguise: it points at the chord that comes next.

## The dominant of another chord

A **secondary dominant** is the **dominant 7th of a chord other than I**: the V7 that belongs to that chord’s own key. It is written **V7/x** (“five of x”). The one on V is the “five of five”, V7/V. In C major:

*The secondary dominants V7/ii to V7/vi in five major keys.*

| Key | V7/ii | V7/iii | V7/IV | V7/V | V7/vi |
| --- | --- | --- | --- | --- | --- |
| C | A7 | B7 | C7 | D7 | E7 |
| G | E7 | F♯7 | G7 | A7 | B7 |
| D | B7 | C♯7 | D7 | E7 | F♯7 |
| F | D7 | E7 | F7 | G7 | A7 |
| B♭ | G7 | A7 | B♭7 | C7 | D7 |

There is no V/vii°, because a diminished chord is not a stable target. In C the notes outside the key are C♯ (in A7), D♯ (in B7), B♭ (in C7), F♯ (in D7) and G♯ (in E7).

## How they behave

A secondary dominant usually **resolves to its target**: D7 → G, E7 → Am. The out-of-key note is the target’s **leading tone**, so it rises by a half step: F♯ → G, G♯ → A. The music briefly leans toward another key without really changing key: a **tonicization**. **Chains** of secondary dominants follow the circle of fifths (E7 → A7 → D7 → G7 → C, lesson 10.4).

A 7-chord on a degree other than V, with a note outside the key, is almost always a secondary dominant. Look at the chord that follows.

## For the bass

The root still moves **down a 5th** (or up a 4th) into the target. The out-of-key 3rd is an excellent **approach note**: over A7 the line moves C → C♯ (the 3rd of A7) → D.

> **Diagram:** The line C – A7 – Dm – G7 – C with roots, and the approach C♯ on beat 3 of the A7 bar. Positions: C fret 3 on the A string; A open and C♯ fret 4 on the A string; D fret 5; G fret 3 on the E string; C again.

## Try it

Play roots of C – A7 – Dm – G7 – C, one bar each. Then on A7 play A C♯ E G and move up from C♯ to D for the Dm.

## New terms

- secondary dominant
- tonicization
- five of five

Page: https://bazzlow.com/en/beyond-the-key/secondary-dominants/