We always pantomime speaking or doing other noise-producing activities. Even in those party scenes where you think you hear us talking in the background, glasses tinkling, etc. Those sounds are added later.
Exception: Sometimes a group of extras will be directed to say something aloud as a group such as a cheer or other group reaction. This is called an omni and the extras are really verbalizing. Unfortunately, union rules exclude omnis from payment at the same rate as spoken lines would be.
Very Interesting.....Thank You
Unless it has been done, there might be a book in this.
LOTS of people Like/Love movies.
You might be surprised.....or i might be wrong

.....how many people would be fascinating to learn about this.
Not only what happens as an extra, but the real experiences, humorous and otherwise, they you have had, or that you learn about from Friends/Coworkers in specific scenes of certain movies.
Not only your experience working, but your knowledge of things like...creating hundreds of people for a crowded stadium.
You probably know a dozen(s) interesting techniques of how movies are made.
I worked in downtown San Francisco in a few of the buildings that were used to make The Game with Michael Douglas.
It was amazing to see how it is all done and how almost nothing that you see on screen is how it REALLY is in reality.
When Douglas walks out of the back door of The City Club Restaurant to find that waitress.....they filmed IN the restaurant.....it is actually the back of a tailor shop, next door, at The Mills Building. Using THOSE stairs allowed them to set up that whole (phony) scene, in the alley, of that old guy collapsing on the street and the ambulance is called.
Anyway............just a thought.
