American music is based upon inventiveness, not classical theory. Primarily blues with very less sophisticated guitarist, compared to today. That's why everyone else in the world brings American music back to America. As Americans we ignore the obvious. A fusion of Classical and American music thought occured slowly around the 1920's. It wasn't clearly defined until the mid '40's. The actual theory came even later. We're barely 50-60 years removed from the thought.

There is no way in purgatory that any reasonable, and being paid musician can function without some form of musical theory. Even though, one can turn on the radio or TV and hear quite the contrary. That's fuel and food for thought.

Fuse just the major and minor pents, and you have Dorian plus 1. Plus modal variations using the same logic, which ultimately wind up to be major or minor scales, from a back door point of view. Chord progressions are just that, chord progressions. They haven't really changed that much in hundreds of years.