I just watched a remarkable TV program on the Public Broadcasting System. It was one episode of "American Masters" and featured David Hockney, a designer of very moving and impressive stage sets. In this program he designs opera sets (such as for La Boehme) trying to undertand and magnify the emotions of the libretto and the music. They were just stunning and the progrtam showed how they built models and then applied the varied choices of mixing lights using a light board so that the lighting technicians could make the sets come alive. It resulted in some static sets being used for three and four scenes because of the flexibility provided by varying lighting from one scene to another.
I highly recommend this program. I read a quote from Laura somewhere where she said she always looked forward to the tech rehearsals where these gifted technical specialists presented their contributions and tuned them to meet the flow of the production. Now I know why.