In the opening chapters of So Faithful a Heart we learn that Nancy has just been hired by His Imperial Majesty, Joseph II of Austria, as the prima buffa (first comedienne), of his newly-formed Italian Opera Company. At the tender age of seventeen, Nancy travels from Venice (with her mother, Elizabeth, as her escort), to accept her position in the Austrian capital of Vienna. Upon her arrival she is given three days to rest and orient herself to her new surroundings before she is to report to the first rehearsals at the Burgtheater.
The opera that Nancy premiered was Antonio Salieri's La scuola de gelosi (The School of Jealousy), in which she took the role of the Countess Bandiera. The plot of the opera involves love intrigues, attempted seductions and provocations to jealousy between members of the three different social strata: the aristocracy, the bourgeoisie and the working class, which was typical for plots in the early to late 1780s.
For the Viennese premiere, Salieri composed a new grand aria especially for Nancy, entitled Ah sia gia de' miei sospiri. It is sung here by the great Italian mezzo-soprano, Cecelia Bartoli.