Which opera  Pelléas et Mélisande and Die schweigsame Frau has fewer acts ?
Pelléas et Mélisande (opera) Pelléas et Mélisande ("Pelléas and Mélisande") is an opera in five acts with music by Claude Debussy. The French libretto was adapted from Maurice Maeterlinck's Symbolist play "Pelléas et Mélisande". It premiered at the Opéra-Comique in Paris on 30 April 1902 with Jean Périer as Pelléas and Mary Garden as Mélisande in a performance conducted by André Messager, who was instrumental in getting the Opéra-Comique to stage the work. The only opera Debussy ever completed, it is considered a landmark in 20th-century music.
Die Schweizer Familie Die Schweizer Familie ("The Swiss Family") is an opera by the Austrian composer Joseph Weigl. It takes the form of a "Singspiel" in three acts. The libretto, by Ignaz Franz Castelli, is based on the vaudeville "Pauvre Jacques" (1807) by Charles-Augustin de Basson-Pierre and René de Chazet. The opera was first performed at the Theater am Kärntnertor in Vienna on 14 March 1809 and was a great success in German-speaking countries in the early 19th century.