Michael Frayn's "Noises Off" shows the influence of three hardy theatrical perennials: the "show-business" play, the "play-within-a-play" and "seven door farce." Perfected by Georges Feydeau in France and writers such as Ray Cooney in England, the seven door farce (an imprecise slang term-they don't always require exactly seven doors) provides the basic structure for this play.