JOAN BAEZ & BONNIE RAITT: Song and social change have been entwined for centuries, from ballads to broadsides that decried injustice. Joan Baez, left, helped define the '60s folk boom not only through her music but also in her ongoing activism on behalf of non-violence, civil rights and political change. A decade later, Bonnie Raitt emerged with an earthier, blues-driven style yet, like Baez, made benefit concerts (including the historic 1979 "No Nukes" concert, which she helped produce) and protest appearances a lifelong commitment. Here, Baez and Raitt appear together at a massive anti-war rally in San Francisco in February, 2003.

(Image: Anthony Pidgeon/Retna Ltd.)