Complex sentence: He was a virtuoso flutist and for a time was the principal flutist of the London Symphony Orchestra, as well being a professor of composition at the Royal Academy from 1926 to 1955.
Split into simpler sentences: He was a virtuoso flutist and for a time was the principal flutist of the London Symphony Orchestra. Alwyn served as professor of composition at the Royal Academy from 1926 to 1955.