For more than half of his long life, composer Roger Sessions was a commanding figure on the American musical scene. He enjoyed the solid respect of his peers, and as a teacher of a generation of composers and author of compelling writings on his craft, his influence on musical thought remains profound. Yet, even in his lifetime, his music endured vastly disrespectful neglect. He was a "difficult" composer. Sessions was well aware of it. In a New York Times article, he wrote, "I have sometimes been told that my music is 'difficult' for the listener. There are those who consider this...