Now that we have the V7 under our belt, we’re ready to dive into the world of secondary dominants. We’ve been imagining the harmonic landscape in terms of a home base, a surrounding neighborhood, and a shadowy area immediately beyond. Today we’re going to enter a portal to another world: the world of chords outside the home key.
Recall that our home key consists of the following chords:
I – ii – iii – IV – V – vi – vii°
Which particular chords these represent depends, of course, on which key we’re in. The following chart shows some common keys:
At this point, we have covered all but the tricky diminished vii (written as vii°). These make up the immediate and surrounding neighborhoods of our home chord, the I. But as songwriters, we are not limited to this small set of chords.
We are free to be adventurous, free to explore other worlds. Playing with secondary dominants will serve as our first step in that direction.
Secondary dominants are dominant chords borrowed from foreign keys. Just as the V can be used to emphasize and anticipate the I, so can a secondary dominant be used to emphasize and anticipate other chords in the home key.
In the key of C, the V is G major. What if we want to emphasize that chord in our song? We can use its own V. Look at the chart: the V of G is D major. But D major is not in the key of C. That’s because the ii of C is Dm. So if we want to play the V of our V chord, we have to play a II chord.
A II chord acts like a portal to another key. It has an unexpectedly bright sound, and noticeably changes the feel of our song. Our environment is suddenly tranformed when we play it. If we use it to emphasize the V, we are using it as a secondary dominant.
It is common in rock and jazz music to play secondary dominants as seventh chords. So in our exercise for today, we are going to play around with the II7.
Remember from last time that the V7 is like a supercharged magnet leading to the I. Well, the II7 is like a supercharged magnet leading to the V. And it will add a whole new color to your songwriting palette.
In order to get a feel for the II7 and the power of secondary dominants, begin by creating a progression that establishes the home key. You can follow any of the methods described in past exercises.
Once you have a progression you like, try ending it with II7-V-I (in the key of C, that would be D7-G-C). Notice how the II7 introduces a bright and unexpected sound into your song. That’s the portal effect.
Now write a melody for your progression. You’ll notice that the II7 will force you to come up with new kinds of melodic ideas. A simple chord change can bring out ideas you’d never have come up with otherwise.
Change things up by replacing II7-V-I with II7-V-V7-I. Notice how the progression from V to V7 sounds very natural here. This is a way of supercharging your magnetic tunnel, building more and more tension and expectation for the I.
- Write a song using only the home key chords and then replace V chords with II7-V pairs. This is a common technique in jazz.
- Try using the II chord instead of the II7 in these exercises. In the key of C, that would be D.
- Create surprise by moving from II7 or II to a different chord than the V. This is a trickier technique, so it will take some trial and error. Try II7-IV first.
Once you’ve taken your first steps into another harmonic world, submit your results as a record for those of us who are still stuck in more familiar territory.