Secondary Dominance

The idea of secondary dominance comes from the idea of using the strong V-I progression (refer back to Harmonizing Scales from another key signature to add movement to your chords. Let's take a standard twelve-bar blues to start.

 
|C7      |F7      |C7      |C7      |
|I       |IV      |I       |I       |

|F7      |F7      |C7      |C7      |
|IV      |IV      |I       |I       | 
|G7      |F7      |C7      |F7      |
|V       |IV      |I       |IV      |

*The IV chord in measure two is a fairly common substitution.

Now what we're going to do in measure eight is take the V chord of G major, (D7) and call this the V/V. Add the V/IV (C7) into the end of measure 9, and the V into measure two.

|C7      |F7  G7  |C7      |C7      |
|I       |IV  V   |I       |I       | 
|F7      |F7      |C7      |C7  D7  | 
|IV      |IV      |I       |I   V/V |
|G7 C7   |F7      |C7      |F7      |
|V  V/IV |IV      |I       |IV      |
 

Already this progression has much more movement in it. However, we can also do the same thing with the ii chord, creating a ii-V-I progression.

|C7        |F7  Dm7 G7|C7        |C7  Gm7 C7|
|F7        |F7  Dm7 G7|C7        |C7  Am7 D7|

|G7  Gm7 C7|F7  Dm7 G7|C7  Gm7 C7|F7        |

Play through this progression, the constant ii-V-I change is pretty common in Jazz, however used a little more selectively can be applied to any style of music, spice up your standard I – IV – V progression in C by playing:

C        Gm        C         F         Am        D         G
I        ii/IV     V/IV      IV        ii/V      V/V       V