Skip to content
19.3 · Cadences & Color

Hired engines

The dominant 7th is harmony's engine: it pushes hard toward the chord a fifth below. Jazz and pop share one trick: any chord can rent that engine. To make V feel important, put V's own dominant in front of it. That hired chord is a secondary dominant, written V/V: "five of five".

Rent an engine for V

The same trip home, twice. In the second pass, plain ii becomes D7, an engine aimed straight at G. Feel the extra shove.

C
Dm
G
C

I ii V I: gentle, fully diatonic.

C
D7
G
C

I V/V V I: D7 doesn't belong to C major (that F# gives it away), and that's exactly why V lands harder.

V of IV: home becomes an engine

The classic C7 → F release is a secondary dominant: V of IV. Home turns into an engine pointed at its neighbor.

C
C7
F
C

I V/IV IV I: the moment C picks up a B flat, it stops being home and starts pushing toward F.

Chain them

Engines can queue: D7 pushes to G7, which pushes to C. Jazz turnarounds are built from exactly this chain of fifths.

Quiz

1 / 3

V/V means…

Score 100% on every quiz and game to complete this lesson.The map of a song →