This is a farce, although a bit high-brow, about what happens when an experimental stage director tries to make an opera ensemble get out on a limb, and do some daring acting. It is soon far too obvious that the two stages are quite different, and even more so the people who walk on them.
The director has a hard time, trying to accomplish anything at all, and chaos is soon at hand. It's a lot of fun, especially for an audience familiar with both the theater and the opera.
Suzanne Osten and Etienne Glaser, the couple responsible for this movie, have a long experience with the theater, where they have been frequently praised for their accomplishments. The movie was a huge hit in Sweden, when it premiered, although it did not seem to have significant lasting qualities. I'm not even sure it was intended to have any.
A somber circumstance, which is hard to label 'trivia', is that this movie was the one Swedish Prime Minister Olof Palme saw, on the night of his assassination in 1986. He was shot when leaving the cinema.