The diminished scale and its lines/arpeggios adds amazing sonic flavors to dominant chord resolving to it’s intended tonic chord. V7–>I. In the key of C, that would be G7 resolving to CMaj.
However, there are other examples of a very similar activity. In the example below, this might come in the form of a blues in G Major. The tonic chord would be G, but in blues is often actually G7. Even if the simpler G major triad is citated, the 4th measure can superimpose the instability of the G7 chord. It is where altered tensions create even more instability, resolving to the IV chord(in this case, C7). Formal music theory labels this as the V7 of IV.
Diminished Scale Blues
If we take G7(spelled G, B, D, F), we find a B diminished triad. The unaltered 9th tension would be A, spelling a G9 dominant chord(G, B, D, F, A). Altering A to Ab, yields a nice resolution to 5th of the C chord: b9 over the G7 chord. This also creates an appropriate environment for the #9 altered tension, the A#(Bb) note. These altered tones will cause the instability that resolves nicely to the IV chord(C). The additional alteration of C#(Db) allows for the Dominant-Diminished scale.
Respelling the chord as Ab, B(Cb), D(Ebb), F(Gbb) yields an Ab diminished chord. Spell the Ab diminished scale Ab, Bb, B, C#, D, E, F, G. From the root note, spell this scale with intervals of alternating whole steps and half steps. Respelling the root of the scale to G, we alternate half steps and whole steps: G, Ab, Bb, B, C#, D, E, F.
Symmetrical Minor Thirds
There are a number of ways to utilize this scale over this chord, including a multitude of arpeggios. As this scale includes a symmetrical pattern of notes, most arpeggios, intervals, and licks can repeat in minor 3rd intervals. For example, the notes of the major triad moved minor 3rds, or every 3 frets on the guitar: GMaj(G-B-D), BbMaj(Bb-D-F), DbMaj(Db-F-Ab), and EMaj(E-G#-B).
The Dominant-Diminished lick below plays over G7. The altered tensions resolve to C7 in measure 5 of a G Major blues. Fill the first 3 measures with any standard blues licks. The G Mixolydian mode, the G Minor Blues Scale, G Minor Pentatonic Scale, G Major Blues Scale, are all available. In the 4th measure, we superimpose the G Dominant-Diminished lick, resolving to a strong note in the C chord at measure 5. Measure 6 also allows for a C# diminished chord. Notice that the C# diminished scale is spelled the same as the F# Dominant-Diminished scale. Fretboard position markers are underneath the notes of the lick, but feel free to play it in any position/fingering that is more comfortable for you.
Click to hear the example:
Now let’s try a Dominant-Diminished lick that works over C7. This lick comes by way of Rick Beato, but we’ll do some customization of it.
Moving In Minor Thirds
We will mainly incorporate diminished chord notes with an additional diminished scale note mixed in. Changing inversions of the lick, the diminished scale note will change to a different note from that scale, yielding the C7 Dominant-Diminished scale(spelled C, C#, D#, E, F#, G, A, Bb). Here it’s in the second position:
Similar to the previous example, a good place to use this over a C Major blues. For the first 2 measures, over the C7 chord, use any blues licks, C Mixolydian, C Blues scale, C Minor Pentatonic scale, etc.
Resolving To IV
At the bars 3 & 4, we’re going to anticipate the IV chord impending in the 5th measure. Generally, the IV chord in this key would be F7. At the end of the above lick, the lick resolves nicely to what may be the C note, the 5th of the F7 chord. Likely the next likely step would be to move to other F7 chord tones, such as a jump to the 3rd of the chord, the A note.
The C13(b9) chord includes altered tensions that sound great when the chord resolves up a 4th to F7 chord. The altered tensions are b9(Db), #9(D#/Eb), and #11/#4(F#/Gb). The 13th/6th is natural rather than altered, as is the 5th of the chord. This makes the scale sound a little more like the blues rather than forcing jazz vocabulary. Disclaimer: I hate that idea. I don’t feel that anything is Jazz vs. Blues. Notes are notes, and I have no issue with using what might be considered Jazz Concepts over a Rock, Blues, or Funk tune.
Notice how this lick starts on strong notes on beat 1 and beat 3, but beats 2 and 4 feature an altered tension opening note. Basically, in the final measure before resolving to the IV chord, we feature the altered tensions on the strong beats 1 and 3. Accordingly, with natural tensions on beats 2 and 4, there is altered tension on the end to resolve the a chord tone in the 5th measure.
The next place to go is to transpose this lick up a minor 3rd. As the Dominant-Diminished scale is symmetrical, play anything from this scale transposed up a minor 3rd(3 frets) and we have all notes from the same scale.
In the case of the example above, we’ve moved all of the notes up 3 frets, which means all of the notes follow the same interval shape with other scale notes. All notes in the scale are a minor 3rd away from another scale note. Any melodic pattern, any note, any arpeggio within this scale can be moved a minor 3rd higher or lower and still remain within the scale tones. The whole scale pattern above can be moved three frets ascending or descending and still remain appropriate within the scale.
We’re at the 5th position, starting on the b7 of the chord, and the 3rd beat starts on a chord tone, the 5th of the chord. Beats 2 and 4 are tensions. In the 4th measure, we start on the 3rd of the chord, which really outlines the chord change, and beat 3 starts on the altered tension b9, but end on the 3rd of the C chord that can lead to the root of the F chord(using enclosure), or resolve down to the b7 of the F chord, the Eb note.
Keep It Moving
Can you see where this is going next? Move the lick up another 3 frets, to the 8th position. All of the notes will still fall within the Dominant-Diminished scale.
Now we find the lick starting on the altered tension(b9), but catching the root of the chord on beat 2, the b7 on beat 3, and the natural 6/13 tension on beat 4. In the final measure before the resolution to F7, we start out with the 5th of the chord, and a strong 3rd of chord on beat 3, but altered tensions on beats 2 and 4. The ending notes form a great enclosure to the 3rd of the F7 chord.
Try taking the first lick on this page and moving it around by minor 3rds. See how it fits with the chord. Some will work better than others. The notes all work within the scale, but how it sounds in relation to the strong chord tones and dissonant altered tensions may be different, depending on how you’re hearing it. You may change the rhythms, change which beat you start on, dynamics, accents, etc.