By now, you should be familiar with 7th chords and how they are built. No? Refresh your memory quickly with this article! Knowing the difference between the different types of these chords will help make secondary dominants make a lot of sense.
Dominant chord recap
The dominant 7th chord’s formula is – 1 – 3 – 5 – b7
It differs from the major 7th with it’s flattened 7th degree, and the minor 7th with it’s major 3rd. The other important thing to note about the dominant chord is it’s place in a given key signature’s diatonic chords. The dominant is always the 5th chord which gives it a perfect cadence to the root or tonic. Let’s look at the diatonic chords of C Major.
| Chord No | Chord | Notes | 7ths | Notes |
| I Chord | C | C E G | Cmaj7 | C E G B |
| ii Chord | Dm | D F A | Dmin7 | D F A C |
| iii Chord | Em | E G B | Emin7 | E G B D |
| IV Chord | F | F A C | Fmaj7 | F A C E |
| V Chord | G | G B D | G7 | G B D F |
| vi Chord | Am | A C E | Am7 | A C E G |
| vii Chord | Bdim | B D F | Bm7b5 | B D F A |
All the chords here contain notes from the C Major scale so there are no sharps or flats. In any key, the V chord is the only naturally occurring dominant chord (in this case a G7). It’s also considered the primary dominant chord of the scale. As mentioned earlier, the dominant provides a perfect cadence to the tonic as it is a source of tension in the key. Once it’s ‘released’ by heading to the chord a 5th below, we hear the resolution in the music.
To get to know what chords are a 5th apart from each other, check out the circle of fifths. Using this can help with figuring out which dominant chord resolves to which tonic. This also work for minor chords!
So we already know that in the key of C Major, the 5th is a G, so the natural resolution from G7 would be to head to Cmajor7.
On to secondary dominants
In the most simplest of terms, a secondary dominant is a dominant 7th chord that is a 5th higher than any other chord except for the I chord. So when there is a single naturally occurring dominant chord, you aren’t limited to using just that one in your songwriting and playing.
Let’s stick with C Major for the time being. As we know, G7 is the primary dominant chord in this key. But if we turned the other chords in the key in to dominant chords, what do we need to do to resolve them? Head a 5th down to that chord’s resolving chord. What’s important to note, is that the secondary dominants won’t be part of the natural key we’re in. So we’ll be playing non-diatonic chords as well as notes outside of the key.
| Secondary Dominant | Notes | Resolving Chord |
| C7 | C E G Bb | F major |
| D7 | D F# A C | G major |
| A7 | A C# E G | D minor |
| E7 | E G# B D | A minor |
| B7 | B D F# A | E minor |
Despite not technically being in the key of C, and therefore non-diatonic chords, you’ll find that these will still work soundly. Check out this link for some examples on secondary dominants in action.
Quick chordal examples
So now we’ll take a look at how we can play a progression that uses a secondary dominant (or more than one!)
Here’s a common I – IV – V – I progression;
C – F – G – C
Normally, you might throw in a G7 before the C at the end of the progression to really hammer home that sense of resolution.
But what if we used a C7 instead?
C – C7 – F – G – C
This could function as a transitional chord at the end of a bar, or taking up a whole bar or more by itself.
In fact, we could add a secondary dominant in front of any of these to add a little intrigue to our progression. So why not throw in one before each chord?
C – C7 – F – D7 – G – G7 – C
There’s a lot of different combinations you can use, so experiment and give it a go!
Secondary dominants are a fantastic tool you can use to add some versatility and spice to your progressions. There’s no reason why you can’t mess around with some tracks you’ve learnt already, give them a little twist.
Of course, as always, please feel free to get in touch if you need some help or would like to give some lessons a go!