Thinking about this in terms of the circle of fifths, there's a lot of representation of the keys that are from 12 o'clock to 3 o'clock, keys C, G, D, A, respec

Thinking about this in terms of the circle of fifths, there's a lot of representation of the keys that are from 12 o'clock to 3 o'clock, keys C, G, D, A, respectively. I think if you looked at jazz standards from the Real Books, you'd see a different histogram, stressing the keys Eb, Bb, F, C. A lot of Western music centers around a tonal center, and then rocks back and fourth on the circle of fifths between IV and V. A lot of pop tunes these days add the vi, further to the right on circle of fifths. In contrast, jazz music tends the move down in fourths a lot, so you see ii-V7-I all over the place, a lot of vi-ii-V7-I, and a sometimes a iii-vi-ii-V7-I. All of these progressions just start some place on the circle of fifths, and then go counter-clockwise until they reach the intended tonal center.