Contents
4. Names and Notations
Now, the II7III7VI7I7VII7 progressions, brought in with such ideas, are called Secondary Dominants.
While V7 is the dominant chord inherent to the key, in a sense, this is the “primary” dominant. The others are created by simply “imitating” V7, so they are given the name “secondary”.
Jazz mostly use them as seventh chords, but in classical music, the triad versions (IIIIIVIVII) are also used, and called “secondary dominants” as well.
- Secondary Dominants
- Dominant seventh chords (other than V7) that resolve by moving to a diatonic chord located a perfect fifth below1.
Theoretically, these chords are considered “borrowed from another key”. For instance, in the key of C major, II7 is D7, which has been brought along as an accompaniment to G. When analyzing the progression D7→G isolatedly, it’s like in the key of G major.
Therefore, in music theory, D7 is understood as a chord borrowed from the key of G major, thanks to the influence of G.
Doubled Dominant
Among secondary dominants, II7 is special in that it progresses to V7, the “primary” dominant chord. II7 is “a dominant seventh that goes to dominant seventh”. Because of this, II7 is referred to as Doubled Dominant.
Variations in Notation
In authentic music theory books, secondary dominants are notated differently.
These notations indicates “what it’s subject to”. For example, I7 is the companion for IV, hence “V7/IV”, meaning “dominant seventh of IV”2.
On the other hand, it is not widely adopted in popular music theory books due to its bulky appearance and the difficulty of quickly identifying the root note. Furthermore, there is an issue with this notation being almost identical to “slash chords”, as mentioned earlier, so this website does not use this notation.
Variations in Quality
In the scores presented so far, the chords after secondary dominants are all triads, such as III7→VIm. However, using seventh chords instead is also acceptable. In fact, it is possible to use consecutive secondary dominants like III7→VI7→IIm. Or as mentioned earlier, secondary dominants themselves can also be turned into triads. Therefore, when it comes to the finer details of chord choices, numerous combinations are possible.
You are free to choose any of these options. Depending on your choice, the character and color of each chord, as well as the semtion connections between chords, may change. So, choose the one that suits the occasion.
Inclusion Relationship of Terms
Secondary dominants can be considered a kind of quality-changed chords. “Quality change” is a broader term, and “secondary dominant” is a special name given to those that satisfy the condition of targeting a prime chord fifth below them.
Classification, Not Rules
So, it’s important not to misunderstand that chords like II7III7VI7I7 must progress to the chord by 5▼. It’s wrong to think like:
Instead,
In other words, secondary dominants are a technique based on something like a decent “basis”, imitating the motion of V7→I, but if taken to the extreme with thoughts like “you need a basis to use non-prime chords” or “music that can’t be interpreted is nonsense,” it’s a misconception of what music theory is.
Especially in genres like rock and EDM, unexpected chord progressions can sound cool, as discussed in nexus theory.
- VImIIVII7
Here, II7 appeared casually without any classical basis. Since it does not adhere to the definition of a secondary dominant, which is “progressing to the chord fifth below”, there is no choice but to simply call it a “quality change”. However, there is no problem with that. As your knowledge grows, you may become hesitant to use unfamiliar chord progressions, so when that happens, I hope you can recall discussions about genres and history to regain the liberated mindset.
Summary
- Dominant seventh chords inserted to target a chord fifth below are called “Secondary Dominants“.
- With 7th added, the increased number of notes connected by a semitone enhances cohesion of the chord progression.
