What happens at the end of Amadeus?

The ending to Forman's film is not the most optimistic of endings.  As the film concludes, Salieri works Mozart to his very end with the composition of the Requiem.  Given his own exhaustion, Salieri takes a moment's rest, during which time Mozart's wife and child return home. Salieri is taken aback by her arrival and even more put off when she banishes him from the home. Upon seeking her husband's confirmation of her actions, Constanze realizes that he is dead.  Salieri looks upon the dead genius with a sense of hollow accomplishment because the death mass remains incomplete.

The film then moves to Mozart's sparsely attended funeral.  Seeing that he was destitute at the end of his life, he was unable to have a funeral befitting his musical talent.  He has a pauper's funeral, with his coffin carried outside of city limits.  A few members of the Emperor's court attend.  Salieri is there, watching his creation drift out of visible range.  The film shows Mozart's corpse being dumped in a mass grave, with a Christian death incantation delivered in a banal manner.  The final chords of the Requiem are heard over a cold shot of Mozart's corpse lying with other unnamed and unclaimed bodies.

The final scene involves present day Salieri laughing at an exasperated priest, who had not bargained for all of this.  The priest's look of shock is only matched with Salieri sardonically noting God's cruelty: "He killed Mozart, and kept me alive to torture."  Salieri argues that he had to watch his music grow extinct, while Mozart's music would live on as the very definition of artistic genius.  As Salieri is taken out of his room for breakfast, he comments to the father that he will be "the patron saint" for all mediocrity, those who lack talent.  He repeats this to the inmates of the mental asylum, chained to walls and locked in boxes.  As Salieri embraces his new role, he hears Mozart's cackle as the film concludes. 

What is the climax in Amadeus?

The play, which opens with the aged Salieri, who has been a successful composer in the Hapsburg court under Emperor Joseph II, addresses the audience in a confession of his having killed the inimitable Amadeus Mozart because of his terrible envy of the young genius's talent. So, because Amadeus is a memory play and the audience is already aware that he has assassinated Mozart, the murder, then, is not the point of highest emotional intensity as it might normally be in a drama. Instead, it involves Salieri's bargain with God that he would live a virtuous life if he achieved fame. 

When the young genius Mozart comes onto the scene and takes from Salieri his glory, the composer breaks his pact with God, and driven by insane jealousy of the young man who composes so delightfully without any effort, as though he were "taking dictation from God," as well as casting Katherina Cavalieri, Salieri’s star pupil in his comic opera, Salieri commits his great sin of pride. Then, the climax, the most moving moment of the play, comes as Salieri in a love for music greater than any other of his emotions, attends Mozart. As Mozart dictates, Salieri writes as quickly as he can, apparently acquainted with taking such dictation. However, as Mozart moves through his composition more swiftly as his genius simply flows, Salieri has trouble keeping up, but frantically writes. When he tells Mozart that he has taken everything down, Mozart says,

Then let me hear it. All of it.
The whole thing from the beginning now!

Impatiently, though, Mozart snatches the pages from him and in a feverish energy, he sings the melodies. "Salieri looks on in wondering astonishment." This scene is quite moving and is the climax, for even in death Mozart has defeated Salieri because the "Requiem" will only illuminate how mediocre Salieri's own work truly is. Should Salieri take credit for this magnificent composition, his fame will be false as he will know the truth himself and still be defeated by Mozart's genius, and still have broken his vow to God.