Secondary Dominants

In the previous session, we learned about seventh chords and expanded our chord vocabulary, but the fundamental base remained the six prime chords. Now it’s time to explore the realm of “non-prime chords”. In this article I’m gonna explain the chords below:

OK, mostly they’re just the sevnth chord versions of what are introduced in the “Quality Change” session. This time the topic is how they’re “justified” in orthodox music theories—Why it’s possible to bring such chords outside the key.

1. The Power of Dominant Seventh

The seventh chord that simply has a “7” as its symbol is called “dominant seventh”. In terms of prime chords, it’s a special chord that only appears when V is in a seventh chord form.

The reason why V₇ is special isn’t just because its chord quality differs from the others. The interval between 3^rd and 7^th being 6 semitones is actually a crucial point.

In the “Two Tones Harmony” article, I introduced the sound of 6 semitones as “creepy”.

Sound of 6 semitones

Due to its highly distinctive sound, 6 semitones is specifically termed as the Tritone.

Tritone Resolution

The “tritone” has a very strong dissonance, and acoustically, it is considered unstable, invoking a desire in the listener’s mind to move towards a more stable chord. So resolving this in the subsequent chord creates a very clear flow of “tension→release”. In the case of V₇, its typical resolution is to I.

This progression is considered theoretically one of the strongest bonds with exceptional clarity, for the following four reasons:

• The root motion is the most powerful and propelling 5^th down nexus.
• It moves from the exciting dominant functioning V to the home base, the tonic functioning I.
• The intense dissonance of the tritone is resolved.
• The strong tendency tones, fa and ti, both smoothly move by a half step to stable tones.

These are the elements that make this progression feel satisfying and powerful. This progression holds a special and crucial position in both classical and jazz music, and in jazz theory it is called Dominant Resolution.

Dominant Resolution

A chord progression from a dominant seventh chord to the chords that can release the tension in a desirable way, typically by 5th down.

In later chapters we examine V7 resolve to chords other than I.

Utilizing dominant resolutions is the key for using non-prime chords in a natural and effective way.

2. Creating Companions – Sharp Series

As I mentioned, V₇ is the only dominant sevenths chords within the six prime chords. This means that only I has its best supporter, the best “underdog” to make itself look good. The other members must be quite envy for it!

II7 : Accompanying V

The seventh chord that progresses by 5_▼ to V is II_m7.

However, II_m7 lacks a tritone, so its connection to V is somewhat weaker compared to the V₇→I motion. Can we somehow strengthen the cohesion?

This is where the dominant resolution comes into play. By forcibly changing II_m7 to dominant seventh, it is expected that we could create a similar acoustic effect as V₇→I.

With this change, two effects are obtained. First, II₇ itself has a tritone dissonance, generating a desire to resolve it in the next chord. And second, the note Fa♯ connects smoothly to So, creating a smoother connection!

The technique of changing II_m to II itself was already introduced. What’s new is that we have created a tritone by adding notes up to the seventh, which has made the sound more complex and the cohesion more powerful. Let’s compare II_m, II, and II₇.

VI_mII_mVI

VI_mIIVI

VI_mII₇VI

The constituent tones are similar, so the difference is not that big. However, a subtle dissonance is added, and while II is just bright and energetic, II₇ has a slightly twisted and funky feel to it. In this style of music, II₇ seems to be the best match.

Example

This is exactly the progression introduced above! The musical style is similar, and II₇ is not only bright but also adds a mature vibes, making it a perfect fit. Though II₇ has Fa#, a tone out of the key, in orthodox theories, it’s appearance is justified as a means to create a good tension/release under the condition that it progress to V.

III7 : Accompanying VIm

The same can be said for VI_m. The accompanying seventh chord is III_m7, but by changing it to III₇, a tritone is generated, and a semitone progression from So# to La is added, making the cohesion stronger.

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Comparison

IV_Δ7VIIIVI_m

This is a typical ballad-like chord progression. By changing IIIm to III, it enhances the emotional appeal. Let’s change this further to III7.

IV_Δ7VIII₇VI_m

The somewhat heightened emotion expressed by the III chord can be further enhanced by making it a seventh chord. In this ballad-style composition, the latter sounds more attractive.

VI7 : Accompanying IIm

And it’s the same for II_m. By changing the accompanying VI_m to a dominant seventh, the cohesion is enhanced.

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Comparison

II_m7V₇I_Δ7VI

II_m7V₇I_Δ7VI₇

The first one is a simple triad major chord, so it feels bright and energetic. In contrast, the latter, when changed to a seventh chord, has a muddier dominant seventh quality, giving it a more mature expression. Depending on the lyrics and melody, both have their merits in this ballad style.

So in a practical sense they’re just the quality-changed chords with 7^th added. But the point is; they can have strong connections on 5_▼ nexus with the power of “dominant resolution”, and therefore allowed to be used since the classical era.

Who Accompanies IIIm?

If we continue in this manner, VII₇ will be introduced as the partner of III_m, but rooted on the seventh degree of the key, it is still exceptional and its significance in popular music is lower compared to others. So I will introduce it later when dealing with VII chords comprehensively, and for now, we will skip it here.

3. Creating Companions – Flat Series

The remaining chord is IV, but the situation changes a bit in this case. The companion chord that connects to IV by fifth down is I_Δ7, and we are changing this to I₇, now the difference between the two is the 7^th note.

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So far sharp accidentals have appeared, but here flat accidentals appears. However, the essence is exactly the same, with the occurrence of the tritone’s dissonance and then the whole tone progression from ti to la becoming ti♭ to la, creating a smoother transition to IV.

Let’s Listen

IV_Δ7III₇VI_m7I_Δ7

IV_Δ7III₇VI_m7I₇

It’s just a change from ti to ti♭, but the effect is immense, creating a powerful force rushing into the IV chord. Placing this chord at the end of a chord loop constitutes a good connection to the next loop.

Examples

The II₇III₇VI₇ progression we discussed earlier has become somewhat familiar through the experience of quality changes, but this I₇ is a completely new face. Let me introduce it with some actual song examples.

“Don’t Stop Me Now” by Queen uses I₇ at the important part of verse, like at 0:16 (“turn it inside out”). The piano plays ti♭ to constitute the secondary dominant. The progression around is II₇IV, the very typical pattern that inserts extra “momentum” going from I to IV.

This case is similar but slightly different, the verse starts with II_Δ7I₇IV. By using major seventh chord you can create a very smooth successive half step motions.

In other cases, VI_m or V is occasionally placed before the set of I₇→IV.