"The history of popular music may be seen as the repeated rescuing of a moribund scene by the music of African-Americans."
So says Donald Clarke in his, for fans of music post 1970, somewhat obnoxious The Rise and Fall of Popular Music. Clarke was actually writing about the mid-nineteenth century but his rule held true until at least the early 1960s and arguably until the late 1980s.
Is it still true, I wonder? And if not, when did it stop being that way?