Book excerpt: A guitarist fires off riffs. A drummer pounds out primal rhythms. Fans scream along to a booming chorus. These are the sounds of rock. When rock 'n' roll first shook up young audiences, parents and politicians screamed in protest. But artists soon used the music to make protests of their own. Since rock's birth in the 1950s, its sounds have been blasted from garages to stadiums. The music can be the soundtrack to rebellion, a tool for self-expression, or just a way to bang your head. Find out what inspired rock pioneers to pick up their guitars. Discover the stories of outrageous punks and grungy alternative rockers. And learn more about legends such as Jimi Hendrix, Janis Joplin, Metallica, and Green Day.