Peter Lorre played Galy Gay in the 1931 Berlin production of Mann ist Mann. The critical response to Lorre's new style of acting was mixed, so Brecht defended the actor's choices in a letter to the Berliner Borsen-Courier, 8 March 1931. It contains some specific insights into Lorre's performance, as well as general methods of acting in Brecht's epic theater. Brecht contrasts "dramatic acting," which presumes a consistent character through a linear plot, with Lorre's desire to show a character constantly changing through a variety of different episodes.
A certain capacity for coherent and unhurried development of a leading part, such as distinguished the old kind of actor, now no longer matters so much. Against that, the epic actor may possibly need an even greater range than the old stars did, for he has to be able to show his character's coherence despite, or rather by means of, interruptions and jumps. [...]Excerpted from "The Question of Criteria for Judging Acting" in Brecht on Theatre, translated by John Willett (New York: Hill and Wang, 1964), 53-57.
The fact that at one point Lorre whitens his face (instead of allowing his acting to become more and more influenced by fear of death "from within himself") may at first sight seem to stamp him as an episodic actor, but it is really something quite different. To begin with, he is helping the playwright to make a point, though there is more to it than that of course. The character's development has been very carefully divided into four phases, for which four masks are employed--the packer's face, up to the trial; the "natural" face, up the his awakening after being shot; the "blank page," up to his reassembly after the funeral speech; final the soldier's face. [...]
As against the dramatic actor, who has his character established form the first and simply exposes it to the inclemencies of the world and the tragedy, the epic actor lets his character grow before the spectator's eyes out of the way in which he behaves. "This way of joining up," "this way of selling an elephant," "this way of conducting the case," do not altogether add up to a single unchangeable character but to one which changes all the time and becomes more and more clearly defined in course of "this way of changing."