With his trademark sunglasses, wide-brimmed hat and antique suit, he strums an acoustic guitar and sings an odd assortment of songs from the early days of the 20th century. At once eloquent and private, in interviews he speaks freely about his musical philosophy but never about his personal life. His recordings sells modestly but steadily, spanning a three-decade career that came into focus with a series of television appearances on Saturday Night Live in the 1970s. A man of mystery who defies musical categorization, his recordings may be found in virtually any bin in the record store.