In this article, I'll show you how to quickly spice up your chord progressions by adding secondary dominant chords. Sounds complicated, doesn't it? It may be at first. But, with a little harmonic theory under your belt, you will find adding one or two secondary dominants an accessible way to add more color, tension and movement to your chord progressions. Secondary dominant chords are not in the tonic key, but work very well as borrowed chords. You will see they have a very familiar sound that you have heard before in classical music or in many Beatles songs (just one of many pop examples) throughout the years.
A secondary dominant chord is the dominant 7th of another chord in a harmonized scale. All chords apply except for the I chord and the diminished vii chord. The I chord already has the dominant 7th chord implied in the scale. If C major is the tonic chord, than the dominant is G7. The other chords and their secondary dominants are outlined below. I am using the tonic key of C Major as an example.
The secondary dominant chord can resolve to its tonic chord to create a key change in a song. Or, it can be used as a passing chord to create more tension in a chord progression and resolve to its tonic chord or not, depending on the composer's wishes. The tri-tone interval between the 3rd and 7th of the chord provides the extra '˜tension' in the secondary dominant chord. This feeling of harmonic tension naturally leads back to the '˜temporary' tonic chord because of the two half step resolutions. You can use a V chord triad instead of the 7th, but the dominant 7th will provide a stronger resolution. Let's look at a few examples.
The most common use of the secondary dominant is in a IV-V-I cadence with the V7/V used before the V chord:
Figure 1: Example 1 - I - IV - V7/V - V7 '" I
MP3 Example 1:
The V7/vi is also nice because it takes you into the relative minor key of the major key where you can stay for a moment before resolving back to major:
Figure 2 : Example 2 - I - ii - V7/vi - vi - IV - V '" I
MP3 Example 2:
Here's an example of the secondary dominant chord not resolving to its tonic but still creating wonderful harmonic color:
Figure 3: Example 3 - I - ii - V7/iii '" I
MP3 Example 3:
I encourage you to play around a bit with these on your own and try some in your compositions. It's easier to start in C major for keyboardists so you can return to all white keys if you get confused. Create charts for yourself like the one above if you want to have a harmonic map of secondary dominants for experimentation. Have fun!