In Boston, Mr. Callahan studied conducting with Atilio Poto and composition with Philip Bezanson and Robert Stern; at Tanglewood, he studied conducting with Leonard Bernstein and Sir Colin Davis. He gained much of his experience conducting many orchestra in the New England area, including the Wellesley Symphony, where he was associate conductor, the Five College Orchestra of Amherst, the Group for New Music, the Tryptich Chamber Ensemble, and the Plymouth Philharmonic; he has also conducted the Tallahassee Symphony Orchestra in Florida.