Those who have seen
this older post know that I am quite the fan of
Amadeus. Recently I was on
IMDB looking up fun facts about the movie, which was adapted from the play by the same name, and they just confirmed the fabulosity of the film. Let me share!
Sets and costumes for the operatic productions were based on sketches of the original costumes and sets used when the operas premiered.
The entire film was shot with natural light. In order to get the proper diffusion of light for some scenes, the DPs covered windows from the outside with tracing paper.
The performance of "Don Giovanni" in the movie was filmed on the same stage where the opera first appeared.
Prague was ideal as a stand-in for Vienna, as modern television antennas, plastic and asphalt had rarely been introduced under Communist rule.
Only four sets needed to be built: Salieri's hospital room, Mozart's apartment, a staircase, and the vaudeville theater. All other locations were found locally.
Several professors of music stated, after studying all of the musical keys struck on pianos throughout the film, that not one key is struck incorrectly when compared to what is heard at the exact same moment. In other words, what you see is exactly what you hear.
During the opening scene, where Salieri is carried through the snowy streets, he is carried past a large extravagant mansion-like building where a party is in progress. According to Milos Forman, this building is, in reality, the French embassy in Prague.
The screen-writer and creator of the play, Peter Shaffer shares his name with the original set designer (for the premier) of Mozart's opera
Die Zauberfloete (The Magic Flute).
When shooting the scene in which Salieri is writing down death mass under Mozart dictation, Tom Hulce was deliberately skipping lines to confuse F. Murray Abraham, in order to achieve the impression that Salieri wasn't able to fully understand the music he was dictated.

Meg Tilly originally was cast as Stanze but tore a leg ligament in a street soccer game the day before she was to film her first scene. Elizabeth Berridge replaced her.
Now go watch the movie with your friends and impress them with your knowledge of the film!