in which a page expresses his love for Barbarina in song.  
Act II of this opera includes the strophic aria "Voi che sapete!" in which a page expresses his love for Barbarina in song.  The act begins with the cavatina "Porgi Amor" in which Rosina prays that her husband will love her again.  Almaviva wants to partake in relations with Susanna, but is foiled when Rosina takes her place in, FTP, what Mozart opera based on a Beaumarchais play about the title character's nuptial affairs?
Act II of this opera includes the strophic aria "Voi che sapete!"
The Marriage of Figaro or  Le nozze di Figaro