The character of Mozart undergoes the most significant change on his way from stage to screen. It is partly due to the influence of Milos Forman, who "envisioned a Mozart figure portrayed as more sympathetic in the film than he was shown in the theatre". (Gianakaris 1985, 92) Peter Shaffer also agreed that it was necessary to "humanize him and make him a more rounded character". (Gianakaris 1985, 92) In the play, Mozart is not nearly so complex a figure as his counterpart and functions as an antagonist rather than a protagonist. His characterisation is a somewhat one-sided and superficial caricature. Shaffer presents him as childish, arrogant, and foul-mouthed; admittedly, he is gifted, but too boorish and impulsive to be successful at the imperial court. He is a genius and "an obscene Struwwelpeter" (Adair, 142) at the same time. Yet, the play does not show Mozart in a bad light altogether. We are presented with a quite ambivalent picture of
Mozart as a child-man. A Mozart with an anal fixation. A Mozart as a permanent adolescent. A Mozart who used foul language, who had a sharp tongue, who was notably ungenerous about his colleagues, who was a womanizer and, at the end, a poverty-stricken alcoholic. But also a Mozart true to himself and his musical vision. Whatever Mozart was as a man -- in his real life as in the play -- in music he was pure. (Schonberg 1980, 1)
Nevertheless, Mozart's positive features are not very convincing in the play, because in comparison to the cinema, the theatre has only limited means of presenting musical genius. This is done much better in the film, and the result is a decidedly more likeable Mozart than we see in the play. On stage, Mozart is mean-spirited and disloyal to his friends. He is vain, conceited, and talks about his colleagues behind their backs or insults them directly:
MOZART: I know what goes on -- and so do you. Germany is completely in the hands of foreigners. Worthless wops like Kapellmeister Bonno!
VON STRACK: Please! You're in the man's house!
MOZART: Court Composer Salieri!
VON STRACK: Hush!
MOZART: Did you see his last opera? -- The Chimney Sweep? ... Did you?
VON STRACK: Of course I did.
MOZART: Dogshit. Dried dogshit. (Play, 40)
He is arrogant and self-assured beyond all measure. Yet his genius is undeniable and, perhaps, gives him the right to consider himself the best composer in the world. On stage, Mozart is also libertine in behaviour and unfaithful to his wife, and shocks audiences with his scatological language and obscene word games. He is altogether a caricature rather than a real man, and he seems a creation of the Devil rather than of God. But we also see Mozart as an inspired composer who is not a mere instrument of God, but a man with his own views about music in general and opera in particular:
[...] all sound multiplying and rising together -- and the together making a sound entirely new! ... I bet you that's how God hears the world. Millions of sounds ascending at once and mixing in His ear to become an unending music, unimaginable to us! [To SALIERI] [...] That's our job, we composers: to combine the inner minds of him and him and him, and her and her -- the thoughts of chambermaids and Court Composers -- and turn the audience into God. (Play, 66)
The film presents him in a similar manner, but adds some scenes that show his character in a new light. On stage, we see Mozart only through the eyes of Salieri; the eye of the camera, on the other hand, gives the impression of objectivity and requires a more naturalistic approach. Thus, for the screen Shaffer had to tune down Mozart's language and behaviour and deepen his character. Through this realistic technique, he presents us now with a man of flesh and blood who "emerges as a conflicted individual, at once obnoxious and charming" (Kakutani, 20). We see Mozart as a rebellious but devoted son, then again as a loving husband and father. The inserted scenes show Mozart "playing an outdoor concert; trying to compose an opera at home while his wife and father argue in the background; kissing his infant son; and clowning about at a masquerade ball" (Kakutani, 20). The introduction of Leopold helps to show the circumstances that led to Mozart's perpetual immaturity, so that his behaviour suddenly becomes comprehensible. We are now able to see Mozart as the ever-innocent and vulnerable victim of his fame, fighting to survive in a world of intrigues and dependencies at the imperial court. He is too honest and straightforward to conform to the falsity of this world, and fails to gain any significant position at court, or even to secure a steady income for his family.
Especially towards the end of the film, the character of Mozart gains depth, as he is simultaneously composing the Requiem and The Magic Flute. In those scenes, Shaffer and Forman "tried to emphasize and dramatize a desperate tension created in the composer by these two emerging pieces, and the opposing worlds they represent: the shadowy and shining kingdoms in collision within one man." (Shaffer 1984, 27)
Tom Hulce's brilliant and vivid performance leads the audience through all the ups and downs of Mozart's short life. At first, he seems just a buffoon, for example in the scene at the wigmaker's shop, and his hiccuping version of the "Mozart giggle" is almost unbearable. Then, however, he develops an unexpected depth of emotion where necessary. He is convincing as a composer, and through his naiveté and suffering in the deathbed scene he manages to move audiences to tears. Hulce's performance is a compelling feat that etches itself indelibly into the memory of the viewer. This partly explains the indignation of Mozart lovers: they realise that whoever watches the film Amadeus once, cannot help forever imagining Mozart as the happy-go-lucky, giggling genius of the film.