Let us first check the first sentence of the refrain of the song ‘Sweet Georgia Brown’ (initial scale C) then we see the chord A7. From there we can conclude that on that moment the temporary scale is D or Dm. (A seventh chord indicates a dominant. And the root of the scale in which he is, is 5 keys to the right. Compare with scale C.) To check weather the scale is D or Dm we can use the melody. It turns out they contain the tones f and b not giving the impression they don't belong to the scale.
a b c# a e e f e a e c# a No gal made has got the shade on sweet Geor-gia BrownClick to hear.
The scale of D = d e f# g a b c# d (in key steps: 2 2 1 2 2 2 1) The scale of Dm = d e f g a b-flat c# d (in key steps: 2 1 2 2 1 3 1)
One has f# and b, the other f and b-flat; none of them has f and b, what we are looking for.
Who knows a solution? It's a pity that everyone looks ahead to the answer. It has taken me some time before I found a satisfying answer. The answer is: it is the scale of D using its own blue note. That is the tone f. Check it out. The blue note is the minor interval above the root note. To understand, compare the scale of C; there the blue note is the note e-flat, because it makes the root C to minor. The blue note has something insecure, because it is a minor element in a major environment. The pianist surrounds it with other notes, either as a chord or as a short melody of tones out of the common scale.
The interesting conclusion of this analysis is that during a temporary scale the blue note of that temporary scale can be used. For a jazzy effect to the blue note of the initial scale the blue note of a temporary scale can be added. Would it be equally successful in every temporary scale?