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Act 3

A rich hall, with two thrones, prepared for the wedding ceremony.

The Count mulls over the confusing situation. At the urging of the Countess, Susanna enters and gives a false promise to meet the Count later that night in the garden (duet: "Crudel! perchè finora" – "Cruel girl, why did you make me wait so long"). As Susanna leaves, the Count overhears her telling Figaro that he has already won the case. Realizing that he is being tricked (recitative and aria: "Hai già vinta la causa!... Vedrò, mentr'io sospiro" – "You've already won the case!"... "Shall I, while sighing, see"), he resolves to punish Figaro by forcing him to marry Marcellina.

Figaro's hearing follows, and the Count's judgment is that Figaro must marry Marcellina. Figaro argues that he cannot get married without his parents' permission, and that he does not know who his parents are, because he was stolen from them when he was a baby. The ensuing discussion reveals that Figaro is Raffaello, the long-lost illegitimate son of Bartolo and Marcellina. A touching scene of reconciliation occurs. During the celebrations, Susanna enters with a payment to release Figaro from his debt to Marcellina. Seeing Figaro and Marcellina in celebration together, Susanna mistakenly believes that Figaro now prefers Marcellina to her. She has a tantrum and slaps Figaro's face. Marcellina explains, and Susanna, realizing her mistake, joins the celebration. Bartolo, overcome with emotion, agrees to marry Marcellina that evening in a double wedding (sextet: "Riconosci in questo amplesso" – "Recognize in this embrace").

All leave before Barbarina, Antonio's daughter, invites Cherubino back to her house so they can disguise him as a girl. The Countess, alone, ponders the loss of her happiness (aria: " Dove sono i bei momenti " – "Where are they, the beautiful moments"). Meanwhile, Antonio informs the Count that Cherubino is not in Seville, but in fact at his house. Susanna enters and updates her mistress regarding the plan to trap the Count. The Countess dictates a love letter for Susanna to send to the Count, which suggests that he meet her (Susanna) that night, "under the pines". The letter instructs the Count to return the pin that fastens the letter (duet: " Sull'aria... che soave zeffiretto " – "On the breeze... What a gentle little zephyr ").

A chorus of young peasants, among them Cherubino disguised as a girl, arrives to serenade the Countess. The Count arrives with Antonio and discovering the page, is enraged. His anger is quickly dispelled by Barbarina, who publicly recalls that he had once offered to give her anything she wanted in exchange for certain favors, and asks for Cherubino's hand in marriage. Thoroughly embarrassed, the Count allows Cherubino to stay.

The act closes with the double wedding, during the course of which Susanna delivers her letter to the Count (Finale: "Ecco la marcia" – "Here is the procession"). Figaro watches the Count prick his finger on the pin, and laughs, unaware that the love-note is an invitation for the Count to tryst with Figaro's own bride Susanna. As the curtain drops, the two newlywed couples rejoice.