Tuesday, June 26, 2007

The Lydian Dominant Mode and b5 Subs

Q: I played through this progression today:


I tried using lydian dominant over the G7 chord and it sounded ok, but not that great. I know its meant to be used over a non-resolving dominant but why??

A: Although I suppose you could use the lydian dominant scale over the V chord, it may not be your best choice. If the V chord in your progression is not altered in any way, it may just be best to stick with the major scale throughout the whole thing (C major for your example progression). The lydian dominant mode of the melodic minor scale is best used over the b5 sub (or tritone substitution if you prefer). Using your original progression as our model, try a Dmin7-Amin7-Db7-Cmaj7 progression using a C major scale over the first two chords and a Db lydian dominant scale (Ab melodic minor) over the Db7. The Db7 chord is the b5 sub, it is a dominant chord placed a tritone away from the V chord.

To give you a simple explanation of why you would want to do this in the first place, substitute another unaltered dominant chord a tritone (b5th) above your V chord: it is to simply create an altered tonality. A Db7 chord placed above a G bass note looks suspiciously like a G altered chord. Look for yourself: Db7/G = G-Db-F-Ab-Cb. Analyze the intervals: G is the root, Db is the b5th, F is the b7th, Ab is the b9th and Cb (B) is the 3rd. You see, the Db7/G chord is really a G7(b5,b9) chord.

Now for a magic trick... What would you play over a G7(b5,b9) chord? That's right, a G altered scale. What melodic minor scale is a G altered mode? It is a Ab melodic minor scale. Remember our b5 sub, a Db7 chord? I told you you would want to play a Db lydian dominant mode over it. What melodic minor scale is the same as a Db lydian dominant mode? Hmm... an Ab melodic minor scale. Do you see the whole picture here? Both the altered V chord and the b5 sub chord are really the same things.

The lydian dominant scale is also commonly used over vamps as well. If you want to learn more about the lydian dominant mode go to these links:

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