XXVIII/10, is an opera in three acts by Joseph Haydn first performed at the Eszterháza palace in Fertőd, Hungary, on 25 February 1781 to celebrate the reopening of the court theatre after a fire.

The main opera house adjoining the palace at Eszterháza had been destroyed by fire in November 1779; La fedeltà premiata, composed in 1780, inaugurated the new state-of-the-art theatre in the grounds which opened after major delays 15 months later.

The libretto was adapted by Haydn and an anonymous colleague from Giambattista Lorenzi's L'infedeltà fedele, which had been set by Cimarosa in 1779.

Haydn had access to Cimarosa's score,[1] although the Neapolitan dialect and crude jokes were removed and the nine characters in the former setting reduced to eight by the conflation of two female roles.

[2] In its revised (and shortened) version, La fedeltà premiata is designated a dramma pastorale giocoso (a comic opera with pastoral elements).

In December 1784, Mozart attended a German-language production at the Theater am Kärntnertor in Vienna,[3] the work of his future collaborator Emanuel Schikaneder.

[5] The first modern performance took place at the Holland Festival in 1970 and the first complete recording was made by Philips in 1976 in association with the Radio Suisse Romande and the European Broadcasting Union.

A garden Young shepherd Fileno laments the death of his beloved Fillide (Celia) killed by a snake.

He is unaware of the fatal penalty awaiting faithful lovers, but Celia, spotting Melibeo waiting to pounce, spurns Fileno to save his life: naturally he is angry and desolate.

A dark wood Melibeo tries to blackmail Celia into the match with Lindoro suggested by Amaranta – she must consent or else die with Fileno.

As he offers himself to the monster, it transforms itself into Diana who accepts the purity and selflessness of his act and for ever absolves Cumae from the fatal curse.

Apart from Melibeo, struck down by Diana's arrows, the opera ends happily with the union of Celia and Fileno, Amaranta and Perrucchetto, and Nerina and Lindoro.

[2] The fright, cowardice and deranged state of Perrucchetto – whose name literally means "wig-maker" – are displayed in his breathless G minor entrance aria, which ends with a request for a bottle of Bordeaux wine.

[1] This blurring of heroic and comic is also seen in the act 2 finale, where Haydn parodies Gluck's chorus of furies from Orfeo ed Euridice.

[2] The work is scored for flute, 2 oboes, bassoon, 2 trumpets, 2 horns, timpani, violins I & II, viola, cello, bass and continuo.