Heard whispers open the play, repeating the words “Salieri” and “Assassin.” A seated man’s silhouette is seen with its back toward the audience. The man is Salieri, retired court composer to the Habsburg emperor Joseph II; he is sitting in his apartment in Vienna. Turning around in his wheelchair, he narrates a confession to the audience, asking it to be his confessor.

Salieri recollects his first meeting with the adult Mozart, even though he had been familiar with the wunderkind Mozart’s music when Mozart toured Europe as a child prodigy, accompanied by his father Leopold. As Salieri muses on Mozart’s music, he reminisces about how Mozart epitomized what Salieri wanted to be: divinely gifted. Instead, Salieri was a mediocre composer, just as history has judged him. Salieri knows too well that the emperor has a tin ear and that Salieri’s politicking rather than musical talent gained him his court appointment.

Mozart arrived in Vienna seeking commissions from the court, where Salieri jealously guarded Vienna’s music scene as if it were his own personal fiefdom. As much as he at first worshiped Mozart’s music as a connoisseur from a distance, Salieri was stunned when he met Mozart as an adult and realized Mozart was as irreverent as Salieri was reverent.

Mozart himself interrupts Salieri’s confession, crudely chasing a girl into the room, at times on all fours, throwing her onto the floor and cavorting with her under the table. His excited speech is filled with playful gutter language, and he acts almost as if he is about to remove the girl’s clothes and make a conquest of her on the spot, although she also appears fairly willing. It is only when his music is heard offstage that Mozart runs off to conduct a performance that the court musicians have started without him. Salieri finds Mozart’s music as beautiful as he finds Mozart himself repulsive and childish. The girl is Constanze, whom Mozart marries against his authoritarian father’s will.

In court, Mozart also makes impromptu variations on one of Salieri’s vapid march themes, greatly enlivening the music, to Salieri’s frustration. Salieri’s anger at Mozart can only grow after the gifted young man seduces Salieri’s young mistress, Katerina Cavalieri, and even she finds Mozart far more interesting than the ageing Salieri. However, Mozart’s marriage to Constanze is mostly a disaster in Salieri’s eyes, as Salieri mocks that he understands her husband’s music far better than does Constanze herself.

Count Orsini-Rosenberg, a Viennese courtier, soon intervenes on Salieri’s behalf in intrigues to keep the emperor’s attention away from Mozart’s opera Le nozze di Figaro: Ossia, La folle giornata (1786; The Marriage of Figaro: Or, The Day of Madness). Mozart has to deal with a court for which he is ill prepared, especially since Mozart is clearly childish in his business and political pursuits, all too often withdrawn from society to compose when he could be performing, and living far more extravagantly than his means.

Salieri pretends to help Mozart, while all the time he is conspiring to hinder Mozart in every possible way, often successfully. Constanze Mozart comes to Salieri for help with a bundle of Mozart’s manuscripts, trying to stave off their financial ruin because Mozart is busy composing profoundly colorful operas such as Die Zauberflöte (1791; The Magic Flute) for Emanuel Schickaneder, an opera librettist and popular Viennese impresario. Salieri reads the musical scores Constanze brings and cannot help but grudgingly admire the beauty of Mozart’s music as he hums or picks out the unsurpassed melodies history remembers well. His admiration turns to astonishment, however, when his examination of the musical scores reveals that they were hastily written without any changes or errors, as if they arrived perfectly complete from Mozart’s head dictated to his pen. Such a compositional process is incomprehensible to Salieri, who repeatedly rewrites his own scores, unsuccessfully editing out as much of their banality as possible. This realization that, despite his childish buffoonery, Mozart appears blessed with divine musical inspiration drives Salieri half mad with bitter jealousy, and he blames God for his mediocrity, as if God were taunting him with Mozart’s genius.

In 1791, Salieri pretends to be a masked apparition of Leopold Mozart and commissions Wolfgang to write a requiem. Salieri intends to steal the music from the soon-to-die Mozart, but his plans are frustrated when the Requiem Mass in D Minor, a moving funerary monument for all time, is kept from him and becomes known as Mozart’s final work of genius.

Salieri finally attempts half-heartedly to cut his own throat, but he mangles even his own suicide attempt, and Viennese society ultimately deplores him all the more for doing everything in mediocrity. Mozart died at age thirty-five in 1791, not from poison but from a complex of medical ills while living in manifest poverty resulting from financial mismanagement. His growing reputation as a tragic genius was strengthened by his burial as a pauper in an unmarked grave. Salieri, however, hovers round Vienna until 1825, barely recognized by society as anything but a dated musical hack whose music was listenable only in his own time.

Shaffer has described Amadeus as “a fantasia on Mozartian themes.” The play is not a documentary biography, but Shaffer asserts that many of the elements of the play are true and that in no way has the specific nature of Wolfgang Amadeus Mozart the man or the composer been violated. On the other hand, one might protest that the Italian composer Antonio Salieri has been slandered by the drama.

The play is set in the imperial Austrian court in Vienna, musically dominated by Italians, foremost of whom is the court composer Salieri, who has pledged his soul to God in hopes of becoming the greatest composer of his age. Salieri has the ear of his emperor, but he is ironically forced by his own understanding of music to recognize a far greater talent in the foul-mouthed, vulgar libertine, Mozart, who is capable of creating music of sublime beauty.

The action is framed by the demented recollections of Salieri at the end of his life, in 1823. He is no longer a famous composer but a forgotten man made bitter and crazy by envy and cynicism. Salieri’s story begins in 1781, when Mozart performs for the archbishop of Salzburg. From that point on Salieri does everything in his power to conspire against Mozart and block his advancement at court. He hires a maid who spies on Mozart and reveals family secrets. After Mozart’s estranged father, Leopold, dies, Salieri, after seeing a production of the opera Don Giovanni, understands the composer’s sense of grief and guilt over his father’s death and devises a demoniac plan that brings Mozart to the point of exhaustion and death.

The set for the play is abstract, a rectangle of wood set into blue plastic. It serves as Salieri’s salon, Mozart’s apartment, reception rooms, and opera houses. In addition, there is an upstage playing space enclosed by a proscenium that Shaffer describes as a light box, a useful device for theatrical trickery. Action originally designed for this space had to be modified for the film adaptation. For the screenplay, Shaffer also had to reinvent the play’s opening, provided by a chorus of voices of the citizens of Vienna. His solution was to begin with Salieri’s slashing his throat, which comes at the end of the original play’s text, and to frame the story with Salieri’s account of his dealings with Mozart. The film version creates a first impression of incoherent madness. The madness becomes more rational and controlled as Salieri tells his story to a bewildered and shocked priest, gradually building in intensity toward a climax of renewed madness. The old, mad Salieri finally calls out: “Forgive me, Mozart! Forgive your assassin!”

Even though the London production of 1979 proved to be the most popular play ever mounted by the National Theatre to that time, Shaffer, ever the perfectionist, continued to revise the play before its New York opening. “One of the faults,” Shaffer notes in the preface to the American edition, was “that Salieri had little to do with Mozart’s ruin.” The American version puts Salieri “where he properly belonged—at the wicked center of the action.” Later still, Shaffer revised the script all over again for the film version, creating one of the most remarkable film adaptations in the history of cinema. The film won eight Academy Awards.