It's hard to describe the particular magic that Joan Baez casts over a crowd in concert. But that enchanting power is captured in this collection, which highlights live gems and rarities from her expansive catalog. Her pure, silvery voice wraps around Bob Dylan's drawl in a delightfully loose-limbed “With God On Our Side.” And when she leads the crowd in an impassioned sing-along of “We Shall Overcome,” it sounds like a revolutionary hymn.