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.
It has been claimed that the concept for Wolfgang Amadeus Mozart's annoying laugh was taken from "references in letters written about him", including a description of him having "an infectious giddy" laugh, and sounding "like metal scraping glass". No citations have been provided for these letters, however. There is no indication as to who wrote them, to whom or when. And in the absence of further citations, these claims of historical evidence for Mozart's laugh should be regarded as dubious at best. Robert L. Marshall, writing in "Film as Musicology: Amadeus" (The Musical Quarterly, Vol.18/2, 1997, p.177) says that there is "absolutely no historical evidence for this idiosyncrasy [Mozart's infuriating laugh]. We simply have no contemporary testimony at all as to how Mozart sounded when he laughed." Marshall goes on to explain that the laugh is a dramatic device, representing the mocking laughter of the gods, as in fact Antonio Salieri recognizes in the script.
When Mozart upstages Salieri by modifying the march that Salieri wrote for the emperor, the modified piece is actually Wolfgang Amadeus Mozarts "Non Piu Andrai, Farfallone Amoroso" from "The Marriage of Figaro".
The "Don Giovanni" scene was being shot in part on the Fourth of July. During one take, upon Milos Forman's call of "Action", a large American flag unfurled from the ceiling. 500 extras stood up from their seats and begun to sing "The Star Spangled Banner". The only extras that did not stand up were about thirty people, scattered throughout the theater- at first thought to be normal people, but it was deduced that these thirty were the secret police.
Several real (or at least apocryphal) events from Wolfgang Amadeus Mozart's life were incorporated into the screenplay, including the interlude between the child Mozart and Marie Antionette, and the Emperor's comment that "Abduction from the Seraglio" had "too many notes".
Milos Forman and Peter Shaffer spent four months adapting the very stylized play into a workable script. They added characters such as the priest, maid, archbishop, and mother-in-law; Wolfgang Amadeus Mozart's character was enlarged beyond Antonio Salieri's perceptions; and Salieri's monologues were reworked visually.
When shooting the scene in which Salieri is writing down the death mass under Mozart's 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.
Elizabeth Berridge, during the Nipples of Venus scene, did not know she could spit out the candy (which was really lumps of marzipan) between takes and ate about 15 whole pieces. She later describes how she thought that they were disgusting and that she eventually made herself sick.
According to Milos Forman's autobiography, one studio offered to provide funding for Amadeus (1984) on the one condition that Forman cast Walter Matthau (a reported Mozart enthusiast) for the role of Wolfgang Amadeus Mozart. Forman refused the offer, considering Matthau to be too old for the role.
According to John Harkness's book "The 1999 Academy Awards Handbook", Maurice Jarre, in his speech accepting the 1984 Best Original Score Oscar for A Passage to India (1984), expressed his gratitude that Amadeus (1984) had not been Oscar-nominated for Best Original Score. An obvious joke, since none of Amadeus' score was original.
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 and Diane Franklin were both screen tested as replacements, with Berridge getting the role.
When the movie won Best Picture at the Academy Awards, Sir Laurence Olivier was presenting the award. He went up to the podium, opened the envelope and said "Amadeus." The problem was he forgot to read the nominees first.
The portrait of Leopold Mozart seen in the movie, while made to look like Roy Dotrice, is based on and has a very close resemblance to a real portrait of Wolfgang Amadeus Mozart's father. The original is in the care of the Mozarteum Foundation in Salzburg.
Baron van Swieten (played by Jonathan Moore) has a Dracula connection. He was the son of Gerhard van Swieten, appointed by Empress Maria Theresia to squelch a vampire hysteria sweeping Austrian society and especially the armed forces. As the Imperial "vampire hunter," the elder van Swieten was Bram Stoker's inspiration for the character of Van Helsing in "Dracula".
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 piece of Wolfgang Amadeus Mozart's music with the oboe and clarinet themes, whose score Antonio Salieri so deeply admires in one of the earliest sequences, is the Adagio, or third movement, of the Serenade No. 10 in B-flat, KV361, also known as "Gran Partita".
As Mozart, having fainted, is carried out of the middle of the opera "The Magic Flute", you see three small boys with wings half following him. This is a reference to the Three Boys (Drei Knaben) who play a significant part in the opera.
The original Broadway production of "Amadeus" opened at the Broadhust Theater on December 17, 1980 and ran for 1181 performances starring Ian McKellen and Tim Curry. The movie was based on the Peter Schaffer play which won the 1981 Tony Award Best Play and who also wrote the movie screenplay. Patrick Hines was in the original Broadway production, but played a different role in the movie version.
F. Murray Abraham originally sought for the small role of Rosenberg. During one audition session, Milos Forman asked him to read for the part of the old Salieri. His reading was so good that Forman has already had in mind of him playing the lead role but deliberately stopped short of saying "you got the part" because Forman knew that casting him for that would clash with his work on Scarface (1983), so he deliberately waited until he nearly completed all his scenes. A few days later, Forman asked Abraham to do the same reading for a few more audition sessions, but his refusal to do so eventually convinced Forman to cast him because he felt Abraham "could be a great actor if there are no brakes in between."
During the start Confutatis section dictation, a miscue from John Strauss (who was cuing the music phrase for both actors via AM wave hearing aids) got Tom Hulce lost and confused because he was waiting for the exact pitch and phrase coming in. The miscue was included in the final film - when F. Murray Abraham repeats the phrase 'A minor', Hulce was not responding for a while as he was actually waiting for the cue.
Salieri's chaste, unexpressed love for Katarina Cavalieri is shattered by the realization that Mozart slept with her. In real life, Katarina Cavalieri was Antonio Salieri's mistress, not Wolfgang Amadeus Mozart's.
The trivia item below may give away important plot points.
The original script for "Amadeus" saw a number of variations in character actions and roles: Salieri's initial suicide attempt saw him attempt to jump out of his bedroom window as his servants tried to coax him away from the window and back to his own room (at which point they, as in the finished film, break down the door and find Salieri wounded); the servant girl Lorl played a slightly larger role as she was Salieri's servant; Leopold Mozart, Wolfgang's father, took a more vehement stance against stopping Mozart's marriage to Constanze; and the Baron Van Swieten was cast as "Von Swieten".