In this episode, I cover all the dominant chords in relation to the I chord. Say for example we’re in the key of C, and there is a D7 chord that moves to G7. This is the V7/V. Nothing weird there. But what about the rare instances when a D7 moves down a whole-step to C Major; Why does that work and what happens to the function of the chord? That’s what I’m going to break down here from I7 all the way up to VII7.
Let’s first start by explaining how the V7 chord and Dominant Function work in a given key.
The progression of V7 to I, Dominant to Tonic, is the foundation of Tonal Music. I’ll use the key of C major just to keep things simple.
In the key of C Major, G7 is the V7 Chord. In this case, the Dominant Chord has Dominant Function as it resolves or has an expectation to resolve down a Fifth.
This chord can be resolved in different ways depending on how it is voiced, but the example below is a very common way to resolve a Root position G7.
The strongest bass motion is down a fifth (G to C in this case). Sometimes this motion is enough to suggest resolution itself.
The B or leading tone resolves up a half-step to C, the root of the I chord and the F moves down a half-step to E, the third of the I chord.
The minor second is the strongest gravitational pull into Tonic that we have. The half-step of 7 to 1 is mirrored in the 4 to 3 motion. 7 to 1 is what defines the Tonality. 4 to 3 is what defines our Modality (Quality of Major or Minor).
While the V7 is the most common Dominant 7 chord, you can have a Dominant chord on any degree move to a I chord. They just won’t have Dominant Function. Some of these cadences are stronger than others so you must use your ears to guide you in deciding if the sound of one of these particular dominant chords is what you want to hear in a given context.
Let's check them out!
#1: I7 or I7#9
This chord has Tonic Blues Function and is considered to be a Tonic chord at rest, despite its Dominant quality. This is what we call a Special Function Dominant which is a Dominant chord that does not resolve or does not have the expectation to resolve i.e. it’s a Dominant Chord that doesn’t have Dominant Function.
Chord Scales: Mixolydian, Mixolydian #9, Lydian Dominant #9, Superimposed Minor Pentatonic, Symmetric Dominant Scale.
#2: bII7
This is what we call a Tritone Substitution, Substitute Dominant, or SubV7. This chord shares the tritone with G7; the notes B and F (The Cb in the Db7 chord is the same note as B, it's just spelled differently). Since the tritone can still resolve in the same manner as V7 to I, it’s a suitable replacement or substitution.
In classical/romantic music it was called an Augmented Sixth chord and came about from a very specific Chromatic Voice leading between two chords.
Chord Scale: Lydian Dominant (the #11 is the root of the V7 chord that it replaces).
#3: II7
This chord comes from the parallel Lydian Mode and it’s another Special Function Dominant; these chords do not resolve or do not have the expectation to resolve. In a Lydian modal environment, it’s a Lydian Cadence Chord. It typically appears on a weak metric stress and returns back to IMaj.
Chord scales: Any form of Mixolydian, or Lydian Dominant.
#4: bIII7
This chord is another Dominant structure with non-dominant function or Diatonic Blues Function. This chord can be used in a blues context as it has a Root built on a blue note.
It can also be taken from the Axis system. This system, which is derived from the Symmetric Dominant Scale, creates a relationship of chords a Minor third apart that all share common tones with each other. In this case, it would be the Tonic Axis starting on our C7 chord and moving in minor thirds to give you C7 Eb7 Gb7 A7 (Bbb7), or
C7 b9,#11
Gb7 b9,#11
Eb7 b9,#11
A7 b9,#11
From top to bottom, the list above reveals the strongest to weakest dominant functions branching off of I7. The A7 is the weakest because Bass Motion of a third is the weakest bass motion and the defining Tritone is part chord sound and part tension (E is a chord tone, but Bb is a b9 tension)
Chord Scales: Mixolydian, Lydian Dominant, Symmetric Dominant
#5: III7
This chord can be looked at in a few different ways.
It can function as a constant structure chord in a blues with a I7 Tonic chord.
You could also make a good case for resolving to a IMaj7 or IMaj6 because this could be a V7/VI resolving deceptively to I. They share a ton of common tones: A-7: A C E G and C Maj7: C E G B and if you use C Maj6 it has all the same chord tones as A-7. It’s more common to see this motion of a Dominant chord down a Major third (In a Minor Key) as V7/I resolving deceptively to bIIIMaj, but it’s the same motion and the principal at play.
Or you can use the Axis System I mentioned earlier, but this time in relation to the V7 chord which gives you G7, Bb7, Db7, E7 (Fb7)
G7 b9,#11
Db7 b9,#11
Bb7 b9,#11
E7 b9,#11
From top to bottom, the list above reveals the strongest to weakest dominant functions branching off of V7. The E7 is the weakest because Bass Motion of a third is the weakest bass motion and the defining Tritone is part chord sound and part tension (B is a chord tone, but F is a b9 tension)
Chord Scale: To be a true deceptive resolution of the V7/VI you must use the chord scale that goes with V7/VI, which is Mixolydian b9, b13. If you are using the Axis System then the Symmetric Dominant Scale is appropriate. In the context of the Blues, any form of Mixolydian or Lydian Dominant or Superimposed Minor Pentatonic.
#6: IV7
In a minor key, it’s a Dorian Modal Cadence Chord which functions as Subdominant Minor. In a Blues context, this has a Subdominant Blues Function, i.e. it doesn’t have Dominant Function as it typically returns to I7.
Chord Scale: Mixolydian
#7: bV7
(I used an inversion for this example for smoother voice leading. In root position the tritone skip in the bass is quite harsh, but is definitely worth playing around with in certain contexts).
This chord is another Special Function Dominant. This chord is used in the blues and has a Root built on a blue note.
This chord can also be derived from the Axis System from the perspective of a Dominant I chord Ex: C7 Eb7 Gb7 A7
C7 b9,#11
Gb7 b9,#11
Eb7 b9,#11
A7 b9,#11
From top to bottom, the list above reveals the strongest to weakest dominant functions branching off of I7. The Gb7 is relatively strong because the defining Tritone is in the chord sound just like the C7 (E(Fb) and Bb are both chord tones of Gb7)
Chord Scales: Mixolydian, Lydian Dominant, Symmetric Dominant
#8: bVI7
This chord functions as an Altered Subdominant Minor Modal Interchange chord… Well, that’s quite a mouthful, isn’t it? But it's not as complicated as it sounds.
bVIMaj7 is the normal Modal Interchange Chord from Parallel Minor and functions as Subdominant, hence Subdominant Minor Modal Interchange, and if you lower or “alter” the seventh degree you get bVI7, hence, “altered.” This can resolve to IMaj7 or I-7.
If this chord cadences to a I7 Tonic then it’s considered to be more of a Subdominant Blues Function.
Chord Scale: Lydian Dominant
#9: VI7
In some rare instances, you may see VI7 cadencing directly to the Tonic chord instead of its expected resolution as V7/II. You can see why it works if you think of it as a jazz reharmonization of a Descending (Chromatically Derived) Diminished Chord which has Non-Dominant Function (Check out my episode on Diminished chords).
If you have a Descending Diminished Chord resolving down a half-step to a minor chord you can reharmonize it as a Dominant chord, which may or may not include the related II-7b5 chord.
Ex: Db°7 | C-7 is reharmonized as E-7b5 A7b9 | C-7
It can also be taken from the Axis System from the perspective of a Dominant I chord
Ex: C7 Eb7 Gb7 A7.
Chord Scale: Some form of Mixolydian (Mixolydian, Mixolydian b9, Mixolydian b9, b13, etc.).
#10: bVII7
This chord is diatonic to Minor key harmony. It’s dominant in quality only and lacks the leading tone of the V7 chord. Its tritone resolution and its upward whole step to the root make it more of an elaborated Subdominant Minor Cadence.
In a Major key, with a Major I chord, this is a Modal Interchange chord or a borrowed chord from Subdominant Minor.
Chord Scale: Lydian Dominant 7
#11: VII7
This chord can function as a reharmonization of the Tonic Auxiliary Diminished chord 1°7 (See my diminished chord episode).
Chord scale: Altered, Lydian Dominant, Symmetric Dominant, or any form of Mixolydian.
Here's a wacky reharmonization idea for you- Instead of reharmonizing with the B7, you can run this B7 through the Axis System and end up with B7 (b9, #11) | Ab7(b9, #11) | D7 (b9, #11) | F7(b9, #11), all of which are possible choices as substitutions for that Auxiliary Diminished chord!
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