One of the most useful post-Bop harmonic devices is the added subV7s. This all purpose device can be used to add more harmonic motion over static or modal harmony, create delayed resolutions, to create smoother transitions into new keys, and to get a little more juice out of boring progressions. It's simple and it sounds quite modern when used correctly.
One of the first guidelines of chord substitution is that you can add a related V7 after any ii-7 and you can add a related ii-7
before before any V7 chord. So if you have one bar of D-7 you can add a G7 after it or
vice versa.
For example:
/D-7 / becomes /D-7 G7/
or
/G7 / becomes /D-7 G7/
Now we can take this to the next step, which is that you can add a related V7 before
ANY CHORD!
You say, "Whaaa?", but yes, it's true. This creates a strong dominant resolution and is a good way to step outside the changes for a second before resolving strongly into the next chord. It should sound very outside while you're playing the added dominant, but as soon as it resolves your ears hears it retroactively as a logical resolution. Once you get the hang of this device you'll soon realize just how often it can come in handy.
In general, when you use added V7s it's a better idea to alter a them a bit rather than to just use a straight dominant chord/scale. This is because the more alterations you add the more momentary dissonance and resolution there will be, also there will be more voice leading into the resolution and the dissonance will sound more reasonable once it resolves.
So if we start with this:
original
/D-7 /D-7 /G7 /G7 /C /
We can do this:
example #1
/A7alt /D-7 D7alt /G7 D7alt /G7 G7alt /C /
scales: (Bb mel-)
(Eb mel-) (Eb mel-) (Abmel-)
We can also think of these added dominants as subV7s (Tri-tone subs), which would give us the these changes
:
example #2
/Eb7(#11) /D-7 Ab7(#11)/G7 Ab7(#11)/G7 C#7(#11)/C /
scales: (Bb mel-)
(Eb mel-) (Eb mel-) (Abmel-)
Now of course these subV7s are going to take exactly the same scales and will be functioning the same as the V7alt chords we added in the previous example, but it may help you create smoother chromatic sounding lines if you think of it this way. I know it does for me.
Now I realize that it may be a lot to calculate at first because you've got to consider the chord you want to resolve to and add a dominant chord a fifth above it before it. Then if you want that added dominant to be altered you have to play the melodic minor scale a half-step above that.......OR if you're adding subV7s you first need to add a dominant chord (with an added #11) and then play the melodic minor a fifth above that to get a Lydian Dominant scale.
Both of these are the same difference in the end:
a fifth + a half-step= minor 6th
or a half-step + a fifth=minor 6th
There's a quicker way to figure out how to find the scale that creates this subV7 sound. Just look at the target chord that you want to resolve to and then before it play a melodic minor scale a Major 3rd below it.
You can also imply a Dominant 7(b9) chord rather than a subV7 by just going down a half-step from the chord you want to resolve to and playing a diminished scale.
Here is what I mean. If you have these changes:
/D-7 /G7 /C /
and you want to do this
:
/D-7 D7(b9)/G7 /C /
You can think about it this way,
the target chord that we want to add the secondary dominant before is G7, so a half-step down from there is F# diminished. This is really just a way to cut down on the time it takes to calculate the correct chord-scales.
I can't tell you how often I use these devices. They sound very modern and hip, and they create a dramatic dissonance that immediately and neatly resolves.
Below is a clearer version of example #2. Click on it to see a large version.
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