"Pop music didn't begin with the Beatles in 1963, or with Elvis in 1956, or even with the first seven-inch singles in 1949. There was a pre-history that went back to the first recorded music, right back to the turn of the century. Who were these earliest record stars--and were they in any meaningful way "pop stars"? Who was George Gershwin writing songs for? Why did swing, the hit sound for a decade or more, become almost invisible after World War...