In the 19th century, Spieloper was understood to mean a light opera genre, developed from Singspiel. Works typical of the genre include those by Albert Lortzing, such as Zar und Zimmermann, and Otto Nicolai's The Merry Wives of Windsor. A key difference between Spieloper and Singspiel on the one hand, and opera buffa on the other, is that the two former genres contain spoken dialogues instead of recitatives, which is why Conradin Kreutzer's Das Nachtlager in Granada and Friedrich von Flotow's Martha do not belong to this genre.