'. . . if one goes by that criterion alone -- that the more people understand it the better -- then one can only reduce the language that you speak in the theatre to the language, for example, of a television series which does take the most reduced language to speak to people: the contemporary shorthand.'-- Joseph Chaikin
Weave all that Exposition into the personal concerns of your Narrator. That means Narrators need to have a real stake in the consequences of the events in the story. Contemporary playwrights hardly ever use impartial and uninvolved observers for this job.
And when Narrators serve this technical function, they're often put in service as Authorial Spokespersons to clarify thematic issues for us. That usually happens toward the end of the play. In the meantime, they dish out the Exposition at important Time Jumps in the play particularly at either side of intermissions.
A rule of sorts: If a Narrator opens the play -- or at least shows up within the first several scenes -- audiences will expect these folks to keep them company on the rest of the journey. The usual places for them to do their
A Few Good Narrators |
http://www.vcu.edu/arts/playwriting/