Of the artists who enjoyed success during the folk music boom of the early '60s, very few have had a career as long and varied as Judy Collins, in large part because she's displayed a stylistic range matched by few of her peers. While Collins is a gifted songwriter who penned a few of her best songs, including "Since You Asked," "My Father," and "Secret Gardens," it's her talent and versatility as an interpretive vocalist that has brought her lasting success. Collins' strong, clear voice has been adaptable to everything from Appalachian folk (1961's A Maid of Constant Sorrow),...