"It strikes me that's what technique must be: the control of the information that
flows from a play to its audience; and in particular the ordering of the information."
I want to talk about point of view in narration. It might help first if we think of a novel as a large packet of information, just like the data packets governed by the hypertext transfer protocol (http) on the internet, which delivers data, order, and destination-- which we can translate for our purposes as story, plot, and audience.
Plot--the ordering, revealing or withholding of information in a story--is especially important in a time-based medium like drama, but also in novels, unless the reader elects to subvert the author's intent by reading the ending first, say, or the author subverts it as in The Dictionary of the Khazars (by Milorad Pavic), wherein he invites the reader to assemble the story in any order they like.
Point of view directs the information spigot in sometimes subtle ways. First it can be can be additive, as in Toni Morrison's Jazz, with multiple narrators slowly bringing the truth into focus, or or subtractive with an unreliable narrator, sometimes severely restrictive, as in the Benjy Compson section of The Sound and the Fury. Even multiple narrators can be subtractive when the different narrators accounts clash so much that we are left at sea.
Which brings us to Someone in a Tree, a tour de force musical number from Stephen Sondheim's Broadway show Pacific Overtures. The show is about Japan's (unwilling) opening to western trade in the late 19th century. Under threat of force, the emperor's representatives set up a meeting with the Americans to devise a treaty. We begin with the Reciter (the uber-narrator of the play) bemoaning the fact that there is no authentic Japanese account of what was said that day in the treaty house. An old man appears.