From its entry on Wikipedia:
Fidelio (Leonore, oder Der Triumph der ehelichen Liebe: Leonore, or The Triumph of Married Love) (Op. 72) is a German opera with spoken dialogue in two acts by Ludwig van Beethoven. It is his only opera. The German libretto was prepared by Joseph Sonnleithner from the French of Jean-Nicolas Bouilly, which had been used for the 1798 opera Léonore, ou L’amour conjugal by Pierre Gaveaux, and the 1804 opera Leonora by Ferdinando Paer (a score of which was owned by Beethoven).
The opera tells how Leonore, disguised as a prison guard named “Fidelio”, rescues her husband Florestan from death in a political prison.
Sounds cheery enough.
Maybe that’s part of the reason why it wasn’t received well when it premiered. Another reason, according to Wiki, was this:
The success of these performances was greatly hindered by the fact that Vienna was under French military occupation, and most of the audience were French military officers. After this premiere, Beethoven was pressured by friends to revise and shorten the opera into just two acts, and he did so with the help of Stephan von Breuning. The composer also wrote a new overture (now known as “Leonore No. 3”; see below). In this form the opera was first performed on 29 March and 10 April 1806, with greater success. Further performances were prevented by a dispute between Beethoven and the theatre management.
Yeah. I can see that.
The other composition on Beethoven CD 11 is Die Weihe Des Hauses, which (in German) translates to Continue reading