For reasons that must await a subsequent post, theatre is thought to require an establishing frame of reference as precondition to the presentation of action. This frame of reference establishes the "reality" in which the action itself occurs; it essentially represents coordinates of virtual space and time. Sometimes, as in the opening Chorus is Henry V, this is done overtly ("Suppose within the girdle of these walls/Are now confined two mighty monarchies," etc.) More often, though, playwright and director can assume the audience will do the work of identifying an establishing frame of reference on its own.
The "work," to be clear about it, consists of the audience agreeing that space and time, for the duration of the performance, will be whatever the play says they are, coordinates which will always, necessarily, be different from the space-time coordinates of the actual performance. The value—even, the plausibility—of the actual coordinates is less important than the act of assignment, which is considered essential to maintaining the so-called theatrical illusion. Theatre says, in effect, "All this stuff you're watching takes place HERE and this place we're calling HERE is really real."
In practice, plays often leave out a lot of specific information about the frame of reference, confident that the audience will not question that the action is taking place somewhere, and that "somewhere" (within the terms of consensual illusion) is "real." Yet in a representational theatre, the fear that everything is based on fragile illusion runs deep. Efforts to erect and maintain a "grounding" reality extend throughout the art form: actor training for example (at least in this country) is based on situating the character in space and time, as if this too would make fiction "more real". And certainly contemporary playwrights (with a few recent exceptions which have stories running inside other stories, e.g., Len Jenkin's A Country Doctor; David Greenspan's Second Samuel II, etc., Daniel McIvor's In on It; Complicite's Mnemonic), are scrupulous about maintain a single, fixed frame of reference throughout the play.
So it's striking that performance is completely free of such baggage. Performance almost always happens in the here and now; actions occur in the same space-time as the audience. Which is not to say that performance is therefore more concrete than theatre. On the contrary, performance typically relies upon its own symbolic grammar to allow any association made vis-a-vis an element or image transmutable into (and transmittable onto) any other image, element or association. The pretense of theatre rests paradoxically upon a non-negotiable assumption that events are "really" happening in some made-up place; performance, paradoxically, presents things "as they are" in order to invite a free play of inference and association. All frames of reference are (by and large) the work of the percipient and thus not only contingent but fluid and mutable.
In BIRD EYE BLUE PRINT, d'Amour and Pearl—frequent collaborators, both with backrounds in theatre and performance—were able to use the theatrical device of establishing frames of reference as an element of the symbolic grammar of performance. The piece took place in an abandoned office suite, and after an introductory prelude, started a space where d'Amour, sitting behind a desk, welcomed the audience to "her space"—a classic instance of an establishing frame. As the piece went on, however, both the identity of d'Amour's character, and her relationship to the physical space, kept shifting. At one point, the audience was led into a "private" room, decorated with various artificial plants, where d'Amour sat on the floor as if in a virtual jungle (the room being simultaneously either a literal or metaphorical extension of the office). At another point, using only sound and vivid, non-realistic light cues, d'Amour shifted the action into a kind of ritual, performed in a virtual theatre space.
The result shouldn't be surprising—if theatre is a cognitive act, then the establishing framework is only an idea, as mutual as any other idea—but the demonstration of it carries enormous implications for a new kind of playwriting, where the action takes place across multiple, fluid frames of reference.
To those who object that several well known plays, e.g. by Pirandello, set the reality of the play equal to the reality of the performance, I would counter that they invariably fail to do so convincingly—and indeed, for reasons outlined in the second footnote, below, cannot do so convincingly by definition.
A moment's thought makes it evident this so-called illusion wouldn't fool anyone over the age of five. "Willing suspension of disbelief" comes closer—since willingness implies both agency and consent—but errs in suggesting disbelief as the default reaction to theatre. Surely it is more accurate to say that theatre is an artificial, conceptual and consensual relationship much like a conversation. The act of theatre requires a cognitive distinction between the words and actions of the people that "in" the play, and the words and actions of everyone else "outside" the play. Theater is only possible inside such a conceptual frame; representational theatre, uncomfortable with its dependence on a conceptual process, tries to "normalize" the framework as an establishing frame of reference.
A fixed frame of reference doesn't prevent the action of the play move around in space and time. Any frame of reference—unless specifically defined otherwise—is presumed infinite. The problem isn't having a scene in New Orleans followed by a scene in Ancient Rome; the problem would be having a scene in Streetcar followed by a scene in Julius Caesar. Strictly speaking, the frame of reference extends far beyond space & time to the mode of the play. It would be like trying to imagine a scene from Streetcar followed by a scene from Streetcar in which someone named Stanley Kowalksi had never existed.
These descriptions are so poor as to be almost useless. The larger problem is that the event was so dependent upon the confluence of text, performance and the manipulations of light and sound in actual space that no verbal description or script excerpt would do it justice. My point is that these things were possible, but you will have to take my word for it.