Book excerpt: Rock music today is universal and its popular history is well known. Yet few know how and why it really came about. Taking a fresh look at events long overlooked or misunderstood, this book tells how some of the most disenfranchised people in a free and prosperous nation strove to make themselves heard--and changed the world. Describing the genesis of rock and roll, the author covers everything from its deep roots in the Mississippi Delta, key early figures, like deejay "Daddy-O" Dewey Phillips and gospel star Sister Rosetta Tharpe, and the influence of so-called "holy rollers" of the Pentecostal church who became crucial performers--Elvis Presley, Jerry Lee Lewis and Little Richard.