I'm trying to figure out something I don't know.
I'm an elementary guitar player. I know how to improvise, I know chord progressions, the circle of fourths/fifths, intervals, etc.
I know I7/IV7/V7, I know that I can mix them. But I realized a problem when I saw John Mayer's "Gravity."
This is my question: Why G major and not G7? Why does he use G minor pentatonic?