I'm begining a "beyond reasonable" amount of investigating in films where a stage performance in front of a live audience is the central theme of the story, especially where the hustle and bustle and preparations behind the scenes activities are portrayed the attending audience is not aware of.
All That Jazz - 1980
Fame - 1980
Cradle Will Rock - 1999
Waiting for Guffman - 1996
The Producers - 1968
Those Lips Those Eyes - 1980
Weeds - 1987
Camp - 2003
Noises Off - 1992
A Chorus Line - I hate to mention it because it's such a terrible movie.
Stayin' Alive - ditto
Hamlet 2 - 2008
Then there are several about the behind the scenes lives of the people,
not so much the hustle and bustle and preparations.
There are countless other films about composers, where the central theme is the performance and composition of their work within the context of their life and culture.
I think below is another documentary that I caught some of a while back. If it's the one or one of the ones I've seen, I remember it being pretty engrossing and fascinating. Wish I'd taken a note of it down, or something. Might be difficult to find though. Looks like even Amazon doesn't have it.