Playing Over Dominant Chords

Q: Like your style.  I need some review of scales to play with regards to how the Dominant Seventh Chord is resolving...functioning as a V chord or just a secondary Dominant (which I would play Mixo or Lydian b7).  If it is resolving to minor I'd play harmonic minor of the letter name of the chord it's going too.

A: here is the basic overview of the dominant scales. Let's take it by how the dominant chord is functioning. When I say functioning, I mean resolving to a I or i chord as in V-I or V-i or G7 - C or G7 - C-7. Non-Functioning means resolving somewhere else or possibly not resolving, as in G7 - F#maj7 or just a static G7 jam. Keep in mind, secondary dominants are for the most part functioning.

Mixolydian vs. Lydian Dominant

Q: I have to play a solo over a C9 vamp, and I realize I have several scale choices. let me see if my theory is correct here: The mixolydian scale is totally diatonic, but the #4 in the lydian dominant scale works because the ear also accepts the blues scale (b5), right? So in a way, the lydian dominant works like a pivot between inside (diatonic mixolydian) and out (blues with b3 as well), which also lets the Dorian work sparingly too. Does that sound about right? (or am I trying to get into heaven here?)

A: You pretty much have it but not completely: Some people would argue that lydian dominant is actually more inside than mixolydian because the natural 4th in mixolydian would technically clash with the major 3rd in the C9 chord. There is some truth in this I think. Technically lydian dominant has no "avoid note" so to speak, the #4 being far enough away from the 3rd in the chord. Some players would tell you, me too for that matter, that mixolydian is better used for a 7sus4 chord. It is all a matter of taste I suppose. C Dorian would only work over a C9 chord because it sort of looks like a combination of the C major pentatonic and C minor pentatonic scale. But it leaves out the most important note, the major 3rd. And it seems clumsy (too big) for blues. So I think that a C dorian scale over a C dominant chord isn't really a great choice. Also, I wouldn't put the cart before the horse, meaning that I wouldn't think that (as you said) a scale is diatonic to a chord, it is really the other way around: chords are diatonic to scales. So C9 is diatonic to both C mixolydian and C lydian dominant. But you are right to think that we like the sound of the b5 because it reminds us of the blues scale (again, a matter of opinion).

Besides the major and minor pentatonic scales, mixolydian and lydian dominant, you can also create some tension by using the half/whole diminished scale.

I've posted on dorian over a blues before. Here>> Other links:

• lydian dominant
• mixolydian
• half/whole diminished
  

triads and the half/whole diminished scale

Q: look at the ii-V-I that I attached, the key is C Major. What is going on over the V chord, G13? I see two arpegios, E major and the other of Db major Why?

A: Yes, this is a trick for the half/whole diminished scale. Actually four triads placed minor 3rds from the root of the dominant chord work well. For example, a G7 chord: G, Bb, Db and E placed over the G7 chord are all good choices for arpeggios. Obviously G placed over G7 would just be the root, 3rd and 5th of the chord. Bb would be the #9th, 5th and b7th. Db would be the b5th, b7th and b9 and E would be the 13th, b9th and 3rd. These are pretty common arpeggios to play over the G7 chord. The sound is from the diminished scale creating a 13b9 and 13#9 tonality. Check here: diminished scale