I've been thinking of Amadeus since Peter Shaffer died last week and came upon this documentary of the making of Amadeus. It's pretty good, from 2002, made 20 years after the film. It has interviews with the actors who played Mozart, Salieri, Constanze, Mozart's wife, and a couple of the minor characters, although I was sorry they didn't include interviews with Christine Ebersole who played Salieri's student (and crush) Katarina Cavalieri, Simon Callow, who played Schikeneder or Cynthia Nixon, probably one of the biggest stars post-movie, who played Mozart's maid. They did include Twyla Tharp and Jeffery Jones (the Emperor) before he was a registered sex offender.
I had heard that Elizabeth Berridge, who I thought was great as Constanze (and director Milos Forman agreed) and who unfortunately hasn't had much big profile film work since the movie, had been cast because Meg Tilly was injured; and that it came down to one other actor and Berridge in the running as replacements and Berridge got the role because the other actor was "too pretty" - what I didn't know was that they gave the reason directly to Berridge herself. She talks about it in minute 32 of the documentary. She also hates marzipan.
I had also heard Tom Hulce had actually played for real in the scene where Mozart is forced to play a piece upside down and backwards.
They make a big deal about how Tom Hulce is not a leading man, but really, he is a very cute man, even cuter with the longish blond hair in the role. He put on quite a bit of weight in the twenty years post-Amadeus. F. Murray Abraham, in contrast, actually looked better in the documentary than he had in the movie twenty years before.
Another really interesting piece from the documentary is the creation of the death-bed/Requiem scene - apparently quite a bit of it was improvised by Hulce and Abraham.