Secondary Dominants

Richard Barrett embarks upon some jargon busting as he explains the mystery behind secondary dominants

Paul McCartney has created some unusual but harmonious progressions using this musical device

Not all chord progressions stay strictly within the diatonic/chord scale convention – and that’s a good thing. Taking a little look at the theory involved here, the C major diatonic/chord scale is Cmaj-Dmin-Emin-Fmaj-Gmaj-Amin-B diminished (Bm7 b5 is also commonly used). These are often numbered sequentially using Roman numerals, so a II-V-I progression in C translates as Dm-Gmaj-Cmaj and so on. The ‘resolve’ from V to I in a chord progression is a very popular move. Let’s embellish it a bit and say the V is a V7, short for dominant 7 – namely a V chord with the b7 added. In C, G7 is the dominant (V7) that resolves to Cmaj (I).

But what if we take this move and apply it to all the other chords in the diatonic scale, and so pretend each chord in the scale (whether major or minor) is chord I and play its V7 first? In the way that G7 resolves to C, A7 would be the dominant to Dm if it were chord I (actually chord II), or B7 to Em (actually chord III). This is known as using a ‘secondary dominant’. More on this below!

Example 1

Using Cmaj as our home key, our first secondary dominant is A7, as this is chord V7 to D. Played between chord I (Cmaj) and chord II (Dm) as Cmaj-A7-Dm, the A7 sets up the Dm in the same way that G7 sets us up for Cmaj. It resolves in asimilar way to playing Dsus4 then Dmaj, as an example.

Example 2

Coming straight from Dm (chord II), our next diatonic chord would be Em (chord III). If we want to insert another secondary dominant here between Dm and Em, we would add B7, which is chord Vin the key of E. So the next part of the sequence would be Dm-B7-Em.

Example 3

C7 is the dominant (V7) in the key of F, so this becomes the secondary dominant, giving us the option of an elegant stepping stone between Em (chord II) and Fmaj (chord IV). Play Em-C7-Fmaj in sequence and you’ll hear the secondary dominant at work again.

Example 4

This D7 is V7 in the key of G, so inserting it between Fmaj (chord IV) and G (chord V) gives us our next secondary dominant idea: Fmaj-D7-Gmaj. We’re pretending the Gmaj is our chord I, leading us to incorporate chords from other keys that sound interesting but harmonious.

Example 5

This E7 is V7 in the key of A, here pressed into service as the secondary dominant to Am, the VI chord. Play Gmaj-E7-Am in sequence and you’ll hear it in action. We’ve only really scratched the surface with these ideas, but hopefully it gives afresh viewpoint on how chords and harmony can work for you in your own compositions.