Day 3 – Secondary dominants
And primary primadonnas! And turbulent turnarounds! And video below!
But first…
1. Secondary dominants
You remember that the dominant chord in a key is the chord built on the 5th degree — the V chord.
In C major, that is G major or G7; in C minor, it is G minor (but we can use G or G7 too); in F major, it is C major or C7, etc.
In Day 1, we saw why the V7 chord, in particular, leads so well to the I chord. The perfect cadence (the V -> I chord movement at the end of a piece) is one of the most common sounds in Western music.
Using this idea, we can introduce new interest in the middle of our song by treating every chord in the progression as a temporary tonic (I chord or i chord) which can be approached by its dominant.
For example, if we have G -> C, we can insert the dominant of G before it — D major or D7 — to get the progression D7 G C.
Assuming we are in C major, it is evident, that D7 is an out-of-key chord (a non-diatonic chord), because it contains F# which is not part of the C major scale (it is actually part of the C lydian major scale, but that’s a story for another challenge).
We know that in C major we normally get D minor (or Dmin7) as the ii chord, so D7 is an odd man out here. We call it a secondary dominant, because it’s the V chord of the chord which follows it.
2. Substituting or inserting passing chords
Secondary dominants are passing chords (we’ll see more of those tomorrow) and as such can be substituted or inserted in a progression to alter its course (and colour).
For example, instead of Am Dm G7 C, you can have A7 Dm G7 C, where A7 is the secondary dominant and replaces Am, or even A7 D7 G7 C, where A7 and D7 are both secondary dominants and replace the usual Am and Dm chords in C major.
Instead of C Am F G, you can have C E7 Am F G, where the secondary dominant E7 is inserted, or even something like C E7 Am C7 F D7 G, where each of the chords in the original progression is preceded by an inserted secondary dominant. (Here is a quick example in the key of D.)
There are two ways to represent secondary dominants with Roman numerals.
The more analytical way is to indicate which chord the secondary dominant is a dominant of.
A7 D7 G7 C in C major can be written out as
V7/ii V7/V V7 I
because A7 is the V chord of Dm (the ii chord in C major), D7 is the V chord of G (the V chord in C major), etc.
The other way is to simply indicate the major or minor quality (and the seventh degree, if there is one) of the chord and the degree it’s built on.
In that case, A7 D7 G7 C will look like this:
VI7 II7 V7 I
If nothing else, secondary dominants show us that in addition to playing around with major or minor versions of a chord, as we saw in the Creep example yesterday, you can also try using the dominant seventh version of the chord.
That’s exactly what happens in rudimentary blues progression featuring the I7, IV7 and V7 versions of what we have come to know as tonic, subdominant and dominant.
3. Turnarounds
Turnarounds function similarly to secondary dominants.
Turnarounds are groups of chords (instead of just one chord) leading up to a certain chord, very often the tonic.
For example, ii V I (Dm G C in C major) is a ubiquitous turnaround in jazz.
V7 IV7 I7 V7 (G7 F7 C7 G7 in C major) is the basic turnaround in bars 9-12 or the blues, cycling back to the tonic at the beginning of the 12-bar loop.
Once you know the target chord, the chord the whole turnaround leads up to, you can use turnarounds the same way as secondary dominants.
Here’s an example of an extended turnaround in the key of C:
Em A7 Dm G7 Cmaj7
You may notice the secondary dominant A7 in there, but there is one more thing. The Em A7 Dm sequence is itself a ii V I turnaround, only the I chord is in fact a i chord — Dm.
In Roman numerals, the analysis can look like this:
ii/ii V7/ii ii V7 Imaj7
By thinking of the ii chord as a temporary tonic, as a target chord for a ii V I turnaround, we are able to string two ii V I turnarounds together into a new turnaround:
iii VI7 ii V7 Imaj7
Of course, you might remember from yesterday that the ii chord in a minor key is in fact a diminished triad (or a half-diminished seventh chord) and the V chord is really a substitute for the v chord. But these technical details can only give you more ideas about possible new combinations.
Here are a few more turnarounds.
4. Homework
You know the drill by now.
Write a song (fragment) using secondary dominants and/or a turnaround.
Try out a new key like D major or D minor.
Share your ideas (or questions!) in the comments below.
Most importantly, have fun!
I’ll see you tomorrow for the lowdown on some more passing and out-of-key chords.
But first:
