After The Great God Brown, Eugene O’Neill turned his inventive mind to related experiments. In Strange Interlude (pr., pb. 1928) he tried what might be called “voice masks”: Each character had a public voice that participated in normal dialogue and a private voice that gave the audience access to the inner thoughts of that character. The soliloquy, used for exactly this type of revelation, was a well-worn device, but it had never been used so extensively before. Despite the risk of prolonging his play by this added dimension, the device was necessary to satisfy O’Neill’s desire to dramatize the conflict between every person’s inner and outer worlds, as he already had managed to do with face masks in The Great God Brown. The “voice masks” were not so difficult for actors to manage as the face masks had been; the audience, too, could more easily accustom itself to the experimental device used in Strange Interlude.

In Days Without End (pr., pb. 1934) the playwright directs that one role be played by two actors, in order to convey the same division of worlds, though here they are finally resolved into one. In More Stately Mansions (pb. 1964), the “voice masks” appear briefly again, in act 2, with extensive soliloquies or asides given by a woman, her husband, and his mother, to expose unspoken dimensions of their fierce rivalry for domestic authority. The exhaustive use of masks in The Great God Brown, however, marked the climax of expressionistic experimentation for O’Neill.

Even as O’Neill turned to more surface realism in his later plays, his basic vision did not alter. Many of his works, early and late, are based on the supposition that it is humankind’s ability to dream that separates it from animal life and offers some hope for an afterlife. Being no romantic, however, O’Neill understood the suffering imposed on humans by that very ability to dream and devoted his most important plays, therefore, to an attempt to distinguish among creative, destructive, and neutral protective dreaming. All these elements are discernible in The Great God Brown.