“One reason for this is that they do not appear on stage. Unlike conductors, who stand in front of an orchestra and wave a baton, they are invisible artists whose work is done when the curtain goes up, and their methods differ so greatly that the art they practice defies succinct definition. Moreover, directors work not only with actors and playwrights but also with the designers of the sets, costumes, lighting and sound for their shows, making it still more difficult to single out their contribution to the theatrical process. It follows that directing should be as hard to teach as it is to define.”