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.
Sieg der Schönheit Gensericus oder Sieg der Schönheit TVWV 21:10 (Hamburg 1722 and Braunschweig) is a comic German-language opera in three acts by Georg Philipp Telemann. It was performed at the Oper am Gänsemarkt, while Keiser was director. Unlike "Orpheus" and "Flavius Bertaridus", the opera contains no Italian-language set piece arias. The librettist was Christian Heinrich Postel.