By rights, Moon Mullican should be a legend twice over, in country music and rock & roll. He merged them both -- as well as blues, pop, and honky tonk -- into a seamless whole at the drop of a hat and the ripple of a keyboard, and also managed to play a seminal role in the history of Western swing, all in a recording career that lasted less than 30 years. Instead, for decades he was one of those "lost" musical figures from the '40s and early '50s, whose career paved the way for rock & roll, who was born just a little too early, and who was a little too old to take advantage of...