"Let's say guitarist Joe Blue invents the blues as we known them in Blue City in 1880. Blue becomes an itinerant musician and travels all over the South. If his music had caught on at home, why would it die out there?" In areas where people try particularly hard to be modernistic, one thing after another (such as use of banjo) can die out there before dying out other places. But of course the Yazoo-Mississippi Delta doesn't qualify as one of those places.