Quote Originally Posted by JonR View Post
When improvising on secondary dominants, the usual scale is determined by the target chord. If the target is major, then the scale on the preceding V will normally be mixolydian (major scale of target). (This applies even if the target turns out to be another dom7 - eg, if D7 in key of C went to G7, we'd still use the G major scale on the D7 - the F# is critical.)
I didn't read it all yet, and have question for this part

So we talk about a myxolydian scale.
However talking about a mode implies the we are hearing a tonic on G, otherwise we could not hear myxolidian. What note we considered as the gravity point is what alows us to hear the mode.
But G is not considered a tonic, not even secondary, so my question is what are we supposed to really hear here then ?
E phrygian from the main tonal center ? G major ?
A chromatic mix of both ?

I agree that while playing a full scale some scale might fit better, but when playing a melody we don't play the scale entirely, so unless the melody gives obvious hints, what can make believe we should hear something or something else ?