The story of American popular music is steeped in social history, race, gender and class, its evolution driven by ephemeral connection to young audiences. From Benny Goodman to Sinatra to Elvis Presley to the Beatles, pop icons age out of the art form while new musical styles pass from relevance to nostalgia within a few years. At the same time, perennial forms like blues, jazz and folk are continually rediscovered by new audiences. This...