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When a dominant chord does not resolve to its I chord, the harmony doesn’t act the way we expect. Therefore, the scale choice for a non-functioning should not be one that sets up expectations of a I chord. We need a scale choice that will not make the listener feel that the I chord is coming; that scale is the Lydian b7 scale. Its formula is 1–2–3–#4–5–6–b7. Notice that all four tones of the dominant 7th are present: 1, 3, 5, and b7.
Try looking at scales as arpeggios with notes in between chord tones. Notice that the 2nd (9th) is between 1 and 3, the #4th (#11) is between 3 and 5, and the 6th (13th) is between 5 and b7.
What is it about the Lydian b7 scale that softens the strong attraction to the I chord? The #11. The #11 is a “disorienting tone” that seems to give the entire Lydian b7 scale an ambiguous effect.
The Melodic Minor Connection
The modes of the melodic minor scale are more useful than the scale itself for use as chord scales over different chords. The seventh mode of the melodic minor scale is also known as the altered scale or the Super Locrian. The sixth mode of melodic minor is identical to the Locrian #2 scale. In this lesson we’ll find another melodic minor connection in relation to the Lydian b7 scale.
Here are the notes of the G Lydian b7 scale.
And here are the notes of a D melodic minor scale.
A side-by-side comparison shows the amazing coincidence.
They’re the same notes! We can say that the G Lydian b7 scale is the same as playing the D melodic minor scale from the 4th degree to the 4th degree. This means that G Lydian b7 is another name for the fourth mode of D melodic minor. Put yet another way, we can say that the G Lydian b7 scale is the same as playing the melodic minor scale up a 5th from the root of the non-functioning dominant 7th chord. For now, we will rely on this way of explaining the Lydian b7 scale/melodic minor scale relationship.
So, over a non-functioning dominant 7th chord, in order to soften the sense of pull to the I chord and create a feeling of ambiguity, you may play the Lydian b7 scale from the root of the V dominant 7th chord. This is the same as playing the melodic minor scale up a 5th from the root of the V dominant 7th chord.
Now you try playing the G Lydian b7 scale over the static G7 vamp. (Download Audio Example)
Clearly not all non-functioning dominant 7th chords are static vamps. Most will be found surrounded by other chords. The next example puts the non-functioning G7 chord in a short progression with another chord. Listen to the example. Ama7 is the tonic chord, therefore we use the A major scale over it. Since the G7 is therefore a non-functioning dominant, we use G Lydian b7 (D melodic minor scale) over it.
Download Audio Example - Download Backing Track
This lesson comes from:
Introduction to Jazz Guitar Soloing