When "Hair: The American Tribal Love-Rock Musical" opened on Broadway, in 1968, it featured one of the best young casts ever to appear in an American musical. Diane Keaton, Melba Moore, and Ronnie Dyson were among the show's stellar performers. The then twenty-two-year-old Keaton, in addition to having a little solo in "Black Boys," was one of the few cast members who didn't shed her clothes in the end. She didn't se…