John Yaffé is an internationally active conductor of opera and symphonic works. He trained in Los Angeles, New York, and Italy; spent 10 years as a coach and conductor in several European opera houses; and has gone on to lead operatic and orchestral performances throughout the U.S. and in both Western and Eastern Europe.   David Daniels is music director of the Warren Symphony and the author of Orchestral Music: A Handbook (Scarecrow, 2005), now in its 4th edition.