What Is Improvisation In The Theatre?

Improvisation is a tool that can teach the actor some of the most valuable lessons of the stage.  These lessons are best learned through some skills classes, such as learning to say Yes to what you receive (a key acting lesson anyway) and also learning how to build on that.  Improvisation is a foundation skill for actors, perhaps it can help them stay in acting fitness, but I doubt its actually use in rehearsal.

Improvisation has been much abused following Stanislavski's attempts at using it to help the actor 'find their character' (I always thought the character was the person in the play, didn't they look there?).  These usually involve long periods of pretending to be someone else doing something else.

Etudes using improvisation are more useful, teaching the actor to do less and still try to achieve something within the imaginary circumstances created for the improvisation itself.