It is usually a diminished scale-C13b9 (diminished whole tone would be wrong as it would imply b13 which wouldn't fit the melody).
The 2 bars of C13b9 are followed by an Fmin chord. I play-
1 bar c13b9 (dim scale) (try playing AMaj triad)
1 bar c13 b9 b13 (super locrian) (try playing AbMaj triad)
The 2nd bar is more tense and moves swiftly to the Fmin chord. This is common with dominants. The trick is thinking about individual movements of guide tones, not just scales.
Jamie O'D
The 2 bars of C13b9 are followed by an Fmin chord. I play-
1 bar c13b9 (dim scale) (try playing AMaj triad)
1 bar c13 b9 b13 (super locrian) (try playing AbMaj triad)
The 2nd bar is more tense and moves swiftly to the Fmin chord. This is common with dominants. The trick is thinking about individual movements of guide tones, not just scales.
Jamie O'D