The Unique Dominant 7th
The dominant 7th chord is a very important chord. Why? One reason is that the dominant 7th defines its key. Let me explain what that means.
Each key only has one dominant 7th and, when a listener hears a dominant 7th, it helps put their ear in that key.
Think of it this way. If you hear a minor 7th chord by itself, you don't know if it is the ii, iii or vi chord in a major key. That minor 7th chord could exist in 3 different major keys. Without more context—other chords around it or a melody—a minor 7th chord's key is ambiguous.
Similarly, if you hear a major 7th chord, it could be a I or IV. It could be in one of two keys.
But, a dominant 7th chord only exists in one key. Hearing it immediately helps establish tonality, or what key you're in.
[The same concept of uniqueness applies to the vii chord but, because of its flatted fifth, you will encounter it less often in most styles.]
Not only is the dominant 7th chord unique to its key, but as we've seen in previous lessons it also has a powerful pull to its related tonic chord.
The dominant 7th is unique and defining of its key, and it is a forward-driving harmonic powerhouse moving us, propelling us, to new chords.
The power of the dominant might be clear to you in the common V to I chord progression, but there are other ways to harness the power of the dominant 7th chord, too.
The “Primary” Dominant
We've discussed the power of the V to I in major keys and the V to i in minor keys. This V chord existing in the key is called the dominant; the I is called the tonic. The I and V love affair is often called the tonic-dominant relationship.
If you simply say “the dominant” you will be understood as saying the V chord in the key.
[In later lessons we will discuss the "functional" names of the diatonic chords. In case you are curious: I=tonic, ii=supertonic, iii=mediant, IV=subdominant, V=dominant, vi=submediant and vii=leading tone.]
No one ever calls the standard V chord in the key the “primary dominant,” but that's what it is—it is the main dominant chord. Understanding it as such will help you understand the topic of this lesson: secondary dominant chords.
Secondary Dominant Chords
Besides the common use of the dominant V chord leading to the tonic I, there is another way we can use dominant chords. We can use them to lead to chords other than the tonic. When used this way these dominant chords are called secondary dominant chords.
A secondary dominant chord, also called an applied dominant, is a dominant 7th chord which does not exist in the current key, but leads us to some other chord in the current key.
Some examples will make this easier to understand, and some audio examples will soon follow below.
How can you get to a C or Cm chord? It can be preceded by its V chord G7 even when G7 does not exist in the key of the song.
For example, in the key of G we could briefly use a G7 chord to get to the IV chord C.
There is no G7 chord in the key of G. G7 contains the note F (G B D F) which does not belong to the key of G which has an F#. Instead, we are momentarily using the G7 from the key of C to get to C.
One more example: Want to get to E or Em? It can be preceded by its V chord B7 even if B7 does not exist in the key.
For instance, in the key of G the B7 chord could be used to lead to the vi chord Em.
Again, B7 (B D# F# A) does not exist in the key of G. The key of G has a D natural, not a D#. Instead, we briefly use the V (B7) used in the key of E minor.
Regardless of the song's key, chords can be preceded by their own V chord. These are called secondary dominant chords.
How the Secondary Dominant Works
The secondary dominant works by harnessing the power of the dominant-to-tonic relationship to drive us to whatever chord we want.
When we hear a dominant 7th chord, we naturally want to hear it resolve to a chord a fourth above. We are conditioned to hear this V to I sound.
Hear C7? It likes to go to F or Fm.
Hear an A7 chord? It likes to go to D or Dm.
Songwriters exploit this powerful V to I sound and temporarily use a dominant 7th chord—regardless of its key—to lead us to where ever they want.
We've examined it in other lessons, but the dominant chord's notes have strong half-step movements between the chord tones. This helps create the strong connection between the secondary dominant and the chord to which it leads.
Common Uses of Secondary Dominants
You will come across secondary dominants in music of all styles. Bach, Gershwin, The Beatles, Willie Nelson, Stevie Wonder, David Bowie, The Eagles, Radiohead, Father John Misty, you name it, there are secondary dominant chords in there. It's a very common harmonic device.
How might you run into secondary dominant chords in a song?
A song could be in the key of G and go: G – Gmaj7 – G7 – C.
In this case, Gmaj7 is the I chord and C is the IV chord in the key of G. G7 shows up in-between as a secondary dominant leading to C. You can hear the tension of the G7 chord dropping you off at the C chord.
Since G7 is the V of C, we would call this secondary dominant the “V of IV” (“five of four”) and traditionally you would write it V/IV.
If you examine the half-step movements within the chord tones of this common progression, you will discover a nice chromatic walk down within the chord tones: G - F# - F - E.
Another example in the key of G might go: G – B7 – Em7.
G is I and Em7 is the vi chord. Even though B is the third in the key of G, the iii chord should be Bm, not B7. So, B7 is not a iii chord, but a V/vi (“five of six”) chord.
B7 is the V of Em7. Note that some may notate this as III7 (a dominant three chord) instead of saying “five of six”. That's acceptable and people will understand, but saying “five of six” is quite clear and how I'd like you to think of it in the beginning.
This progression, like many satisfying progressions, also contains chromatic movement between the chord tones: D - D# - E.
A final example in the key of G: G – Am – A7 – D7.
Here we have the standard minor ii chord (Am) followed by a dominant chord built on the second note of the key (A7). Once again, the A7 is a secondary dominant. A7 is the V of D7 (“five of five”). This is one of the most common secondary dominant chords you will find.
This progression also contains chromatic movement between the chord tones. One chromatic path is: B - C - C# - D.
So, we can temporarily use the V of wherever we are headed to create more tension and lead us to that chord.
Now when you see a dominant 7th chord not built on the V of the key, look to where it resolves. Does it resolve up a fourth? If so, you've found a secondary dominant. If you didn't know about secondary dominants, you might mistakenly analyze a V/vi as a iii chord, or a V/V as a ii chord. Now you know better.
Common Secondary Dominants
Here are some secondary dominant chords you will commonly encounter:
|Secondary Dominant||Key of C|
|V/V||D7 – G7|
|V/ii||A7 – Dm|
|V/IV||C7 – F|
|V/vi||E7 – Am|
|V/iii||B7 – Em|
Is a Secondary Dominant a Key Change?
While the secondary dominant is from another key, it is not usually thought of as a key change. Secondary dominants are typically brief transition chords between otherwise diatonic chords in the key of the song. There could, however, be grey areas where one could argue the key has in fact changed. We will discuss key changes in future lessons.
Deceptive Secondary Dominant Chords
While most secondary dominant chords resolve up a fourth as explained in the above examples, some can resolve elsewhere. These are called deceptive secondary dominant chords. That is, they don't resolve up a fourth like you expect. Sneaky deceivers!
In the case of deceptive secondary dominant chords, they will connect to chords related to the expected chord a fourth above.
Here is an example of a deceptive secondary dominant:
V/vi to IV
You would expect the chord B7 to resolve to an E or Em chord. B7 is the V of E and Em. But, B7 could also resolve to C. Why? Because C and Em share notes in common. C = C, E, G and Em = E, G and B. Two of the notes (E & G) are the same. That means those smooth half-step connections we've discussed happen between B7 and C like they do between B7 and Em.
You can start to imagine how many possibilities this opens up. Don't let them overwhelm you. As you grow to understand the inner workings of these progressions you will understand them in more general ways and the number of possibilities won't seem as overwhelming.
I will explain repeatedly that the foundation of all interesting chord progressions is the chromatic half-step connections between the chord tones. (I told you early in the lessons that chord tones are primary!)
Bass Players and Secondary Dominants
You may be wondering who is responsible for adding or applying the secondary dominant in a song: the songwriter, other instruments or the bass player?
Often the secondary dominant chords are written into the song and all the musicians play and address them.
In other instances, the bass player can imply and play them even if the rest of the band does not. The power of the resolution is so strong it works even if the other instruments ignore it. A bass player can create harmonic momentum underneath everyone else. By now you should know the power of the bass.
For example, the band may play G – G – C while the bass player plays G – G7 – C. Or, the progression may go Am – Am – Dm and the bass player can imply an A7 chord (Am – A7 – Dm) without breaking anything.
Implying the Secondary Dominant
As a bassist, how do you imply or emphasize the secondary dominant? Play or emphasize the flatted seventh of the secondary dominant if the rest of the band is not throwing it in. If you stress the note B♭ under a C triad, you are creating a C7 chord.
In a minor progression like Am – (A7) – Dm, you can additionally emphasize the third of your implied secondary dominant since it is changing from a minor third (C) to a major third (C#).
Essentially you are emphasizing the notes not in the key. With time, this will start to sound natural to you.
Let's look at a simple example:
Here is the most basic I and IV chord progression in the key of C. The first two times I play the roots. In the second half I slip in a B♭ note implying the 7th of a C7 chord (V of IV) on the way to F. You can hear the added tension connecting to the F chord.
On the F chord I sneak in notes outlining the regular V chord G to bring it back to C.
You can hear how, even though the guitar and piano keep playing plain C and F chords, the bass adds extra harmonic motion between these chords and doesn't upset anything. Pretty cool, huh?
The famous Motown bassist James Jamerson is a master of this harmonic technique of implying V chords throughout his basslines. See the song examples for this lesson.
I Still Don't Get It!
I will repeat, if after this lesson the idea of secondary dominant chords is still a mystery to you, don't worry. You can come back to it. Just realize that many songs are mostly diatonic with some outside, non-diatonic, chords thrown in to make things more interesting. Knowing this will help you be less confused as you start to analyze the chord progressions of your favorite songs.
Exercises, Songs and a Quiz
I've included several exercises showing basslines applied to secondary dominant chords.
There is also a list of song examples to listen to and optionally learn to play. And, I've included a quiz to help you test your new knowledge of secondary dominant chords.