Same-note scale choices

[mjlee25]

I know this has been discussed before, but I still dont' quite understand: As an example, say I'm improvising over a static dominant chord. In this case mixoldyian is the obvious choice, though many recommend dorian with the root on the ii chord (e.g. A dorian over a D7.) D mixo and A dorian are the same notes of course. So why is Dorian on the ii mentioned as an alternative? Is it because the finger patterns many of us use for the 2 scales are different, so we often come up with different sounds and licks?

[ragman1]

Is it because the finger patterns many of us use for the 2 scales are different, so we often come up with different sounds and licks?

Essentially, yes. The different patterns produce a different effect.

Chord tones are the strongest notes. If they're centred on the D7 you're likely to hear the D, F#, C, E, and so on. If they're centred on the Am7 (when the D7 chord is playing) then you're going to hear a lot of extensions of the D7 chord like A, B, G, E, and so on.

You probably need to put on a D7 chord as background and experiment with the two types. The effect you want to produce may well depend on the kind of tune you want them for. Both are effective but the two kinds make for different feelings and reactions on the part of the listener.

[rpjazzguitar]

I'd argue that once you know the chord tones and the tonal center, you don't need to worry about the difference between A dorian and D mixolydian.

That is, you can put the chord tones on the strong beats if you choose, because you know what they are. The remaining notes in the modes are all within the tonal center.

This applies to a simple harmonic situation like a ii V I.