I hate having words put in my mouth.
Those are not the ONLY scales compatible with those chords:
Just to name a few:E Neopolitan minor, A Ethiopian Geez & Ezel
G Dominant 7th Scale, etc.
WOW!!! Sounds..... impressive?..... but again I must disagree.
I stated that
The only diatonic scales that would fit this progression is A minor or C major.
Your mentioned "scales" don't quite fit that description. A Ethiopian is the same as A natural minor or Aeolean. Ethiopian Scale and Others G Dominant 7th scale is the same as Mixolydian (as far as I can tell) and contains the same notes as C major.
E Neopolitan minor is a synthetic scale because of it's construction and therefore non-diatonic. Neo. Link Notice the distance between the A-flat and the B-natural are more than a whole step. Not to mention, with E as a root that scale contains a D#. This would sound terrible if a less experienced player landed on that pitch during a solo.
Guitarist spend too much time with their panties in a wad over 50,000 scales and Mel Bays 1,000,000 chords.
I tell my students all the time to simplify their thinking and worry more about the sound of music. Theory is very important but, music came first and theory second.
Who gives a crap if C major and A minor start on different notes. When you improvise you don't always want to start on the first note of a scale, do you?
