The Diminished Scale, often considered the Whole-Half Scale, which we can us over a Dominant 7th chord, considered to be the Half-Whole Scale. This is clearly the same scale, starting from a different note in the scale. As we know the scale is symmetrical, or the same intervals, ascending or descending through the scale, we can utilize interval patterns to move around. In this example, we’re going to play over a G7 chord. However, as the scale is symmetrical, any pattern we play over the chord can be moved a minor 3rd higher or lower and will work over the same G7. These patterns will also work over chords a minor 3rd higher or lower, so all of these patterns will work over Bb7, Db7, or E7 as well as G7. 

Building the Dominant-Diminished Scale

This scale has altered tones, so we’ll fit it particularly well over the Dominant 7th chord that will be resolve down a fifth to it’s intended tonic chord. The alterations in the scale will work well with the chord tones, but will include a b9, #9, #11, along with a natural 13 and the chord Root, Maj3rd, Perfect 5th, and Min7th. Here are the notes of the G Dominant-Diminished Scale:

G->Ab→Bb->B→C#->D→E->F→G

This gives us, from the Root note(G), a Half Step, then Whole Step, Half Step, Whole Step, etc. Due to this symmetrical nature of the scale, we could consider the scale pattern to be a series of whole step intervals, separated by half step. 

Ab→Bb(half step)B→C#(half step)D→E(half step)F→G(half step)Ab→Bb

Useful pattern in Dominant-Diminished

Mike Stern teaches a melodic pattern taught by pianist Kenny Kirkland. To play this pattern, let’s first look at the scale over two octaves: 

    (W)     (W)      (W)   (W)      (W)      (W)     (W)    (W)

Ab→Bb B→C# D→E F→G Ab→Bb B→C# D→E F→G

Now, the Kenny Kirkland pattern makes this work on the guitar pretty well. To do this, we will play the first Whole Step interval, Ab→Bb, then skip the next Whole Step, B→C#, and go straight to the next one, D→E. This is a pattern of two Whole Step intervals an augmented 4th apart. We then ascend a half step and play the same pattern. Listed in horizontal fashion, we spell it like this:

    (W)     (W)    (W)    (W)     (W)      (W)

Ab→Bb D→E F→G B→C# D→E Ab→Bb

Make it work on the guitar

To make this fit into a guitar position system, we can start in the 4th position, using fingers1 & 3, switching to fingers 2 & 4, then changing position by 1 fret to use fingers 1 & 3 again, alternating to fingers 2 & 4, 1 & 3, 2 & 4: 

This utilizes all of the scale notes, but avoids running up and down the scale in order. We can also play this lick starting at the 7th fret, the 10th fret, or the 11th fret. Also, we can use this lick at any of those locations on the neck over G7, Bb7, C#7, or E7. Use this also over Ab^o7, B^o7, D^o7, or F^o7.