In other posts, I have talked about how strongly a V7 chord leads into a I chord. It creates the strongest cadence – the strongest feeling of arriving home. Jazz musicians have latched onto this idea and decided to use it more generally; they will often lead into a chord in a progression by going through a “secondary dominant.” In other words, they will play the V7 of the chord that they are going to, as a transition or even as a substitution for the preceding chord.

Rule You can approach any chord in a progression by playing the V7 of that chord. This rule is directional, and not commutative.

Example: Suppose you have a progression that goes from E to G. If you wanted, and it fit the melody, you could split the first measure, and play E D7 / G.

Or, there are situations where you might want to omit the E entirely, and simply play D7 / G. Or perhaps, you want to delay your introduction. You could play, instead, E / D7 G.

Notice in these examples that I am introducing the G chord with the dom7 chord in the key of G. Since we don’t have the full progression, we don’t even know what key the song is in, and it does not matter. This substitution always uses the dominant 7 of the target chord (meaning you think of the note of the target chord as the temporary “key” and play a dominant 7th chord into it.)

Corollary You can make a substitution for the V of chord you are introducing.

From the last topic (which was a long time ago, I realize), a common substitution for a Dom7 chord is the b5 substitution. In the above examples, this would mean you would have E / Ab7 G. Or simply Ab7 / G, etc…

Second Corollary You can introduce your Vof… chord with another Vof… chord.

Since any chord can be introduced by a Vof substitution, so can a Vof chord. Thus, in our example, you could play E A7 / D7 G. Or using a b5 substitution, perhaps E A7 / Ab7 G, or E Eb7/ D7 G.

The second corollary leads to what jazz musicians call “back cycling,” where you cycle through a fair amount of the circle of fifths to get to the target destination. Also, note that by using lots of b5 substitutions you can simply walk down chromatic seventh chords, however long you like, to reach a target chord.

So if you have a target chord of Cmaj7, you could go B7 E7 A7 D7 G7 Cmaj7. Or F7 E7 Eb7 D7 Db7 Cmaj, or any other variation.

As a result, it becomes very important to try to learn the circle of fifths: C F Bb Eb Ab Db Gb B E A D G C

Finally, you are not limited to 7th chords in your substitutions. You could also do a ii-V substitution for a Vof… chord, or any other substitution that fits (which is a matter of your ear and taste). For example, instead of E / D7 G, you could do E / Amin7 G, or E Amin7/ D7 G, or E Amin7/ Ab7 G, etc…

I am attaching yet another version of Amazing Grace to give more detailed examples of the Vof… or secondary dominant substitution. This time, I have not put the explanations in for the chords I am using. So it’s either up to you to ask for the justification for a chord, or to ask me.

I will have two more major topics in this series on Chord Substitutions, and when I am done, I will post some 12 Bar blues progressions which make use of these substitutions, if people are interested.

As always, feel free to ask any questions you might have.