By 1961, Joan Baez, the dark-haired waif who had captured the spotlight at the first Newport Folk Festival just two years earlier, was folk music's virginal superstar, leading the coffeehouse culture of a new American generation. And an unknown, unwashed, Woody Guthrie—worshiping kid from the Minnesota suburbs named Bob Dylan had just arrived in Greenwich Village. In an excerpt from his forthcoming book, Positively 4th Street, DAVID HAJDU recalls the prickly beginnings of the Baez-Dylan relationship, the strange symbiosis between her voice and his music, and the triumphant, magical appearance at Freebody Park that made musical history