Willie Dixon's life and work was virtually an embodiment of the progress of the blues, from an accidental creation of the descendants of freed slaves to a recognized and vital part of America's musical heritage. That Dixon was one of the first professional blues songwriters to benefit in a serious, material way -- and that he had to fight to do it -- from his work also made him an important symbol of the injustice that still informs the music industry, even at the end of the 20th century. A producer, songwriter, bassist, and singer, he helped Muddy Waters, Howlin' Wolf, Little...