To conductor James Levine’s way of thinking, there is plenty of important American music from the 20th Century that never had fair hearing. So he looks upon his new appointment as director of the Boston Symphony as a way to do something about it. “One of the principal attractions for Levine is that he will finally have the opportunity to serve as an advocate for contemporary music, and American music in particular. For him, this has been a lifelong commitment, but none of his previous positions has enabled him to pursue it fully.”