Zaide (originally, Das Serail) is an unfinished German-language opera, K. 344, written by Wolfgang Amadeus Mozart in 1780. Emperor Joseph II, in 1778, was in the process of setting up an opera company for the purpose of performing German opera. One condition required of the composer to join this company was that he should write a comic opera. At Salzburg in 1779 Mozart began work on a new opera (now known as Zaide although Mozart did not give it such a title). It contains spoken dialogue, which also classifies it as a Singspiel (literally, “singing play”). Only the arias and ensembles from the first two acts were composed. Missing are an overture and third act.

https://en.wikipedia.org/wiki/Zaide