CHORDS THEORY - Lesson 10 - Chord substitutions

Andrei Moraru

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Nov 11, 2019
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So is this similar to football where players get substituted when they are fatigued? Can chords get chord fatigue?
  1. Topics of discussion
  2. Diatonic chord substitutions
1. Topics of discussion

In this tutorial, we are going to talk about chord substitutions which you can use in your chord progressions. So, let's have some fun.

2. Diatonic chord substitutions

A chord substitution occurs when we replace a primary chord with a secondary chord that can play the role of the primary chord which it is replacing.

So, how does one figure out which secondary chord replaces which primary chord? It's something like this:
  • the chord located a third above a primary chord can be used to substitute it
  • the chord located a third below a primary chord can be used to substitute it
What this translates to is the following:
  • the I, iii and vi chords can be used as tonic chords
  • the IV, vi and ii chords can be used as subdominant chords
  • the V, vii and iii chords can be used as dominant chords
"Wait, what? But there are some chords which can play both roles...what gives?"

So...how does this work? How do we know what type of chord we are substituting? And how does this help our progressions?

Obviously, whenever we are substituting chords, we are of course adding our own twist to the song. As you can see, the ii and vii chords have an obvious role, in that they are a subdominant chord substitute and a dominant chord substitute respectively.

As for the others, they serve the purpose of allowing you to extend your chord progression. And the role that they play in your progression is determined by the chord played before them.

For example, if we were to play a chord progression like I-iii-IV-V, then the iii chord is used as a tonic substitute because it is played after the I chord. However, if we are to play a I-IV-V-iii progression, then the iii chord would be acting as a dominant chord substitute because it is played after the V chord.

Aside from the obvious ones, let's take a look at the progression from the previous tutorial: I-V-vi-IV. What kind of a role does the vi chord play here? The answer is a tonic substitute, because it fits the description, with the vi degree of a scale being located a third below the tonic note, if you look at it as subtracting a third from the root note.

The same can be said for this progression: I-IV-iii-V. The iii chord acts as a tonic substitute because it fits the bill, what with the iii degree being located a third above the tonic note and such.

That about covers it for this one. Next time, we will meet up in the Intermediate Theory sections, when we talk about major 7th chords. See you then.
 
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