Czech-based musicologist claims to have found missing libretto to Mozart's Zaide

For many years Wolfgang Amadeus Mozart's operatic work Zaide was regarded as a fragment. More than an hour of music was preserved but that was only the arias. Originally they were linked by spoken text, none of which survived. The German musicologist and conductor Andreas Kroeper, who now lives in the Czech Republic, says he has found the missing text and has proved it belonged to Zaide.

Mozart started to compose the two-act Singspiel, set in a Turkish harem - a popular setting at that time, some time around 1780 in Salzburg. The libretto, developing similar plots of the period, was written by the Salzburg court musician Johann Andreas Schachtner. But Mozart soon realised a serious piece like that would not go down well with the Viennese audience whose tastes had turned to comic operas.

Mozart abandoned the project, not finishing the overture and the final act. Zaide was not staged until 1866 in an adaptation. Further adaptations followed, often with a narrator filling the gaps between each musical number. The British Classical Opera Company recently decided to commission a contemporary poet to write new lyrics and to use other works by Mozart from the same period to complete the piece musically. In the Czech Republic, Zaide was adapted by the South Bohemian Theatre three years ago with actors outside the plot carrying the storyline from on sung piece to another.

In 1936 the Mozart expert Alfred Einstein found a libretto believed to have been the inspiration for Zaide. He compared it to the fragment, found the comparison unsatisfactory and abandoned this track. The Czech-based musicologist and conductor Andreas Kroeper says this was a mistake. He says that when examining the libretto thoroughly he found it had been used as a model for Zaide. He believes Mozart and Schachtner took liberties with the original version, left out some parts and changed the order of scenes.

Andreas Kroepner has now prepared a preview of the completed Zaide and hopes to stage it in Europe, the United States and Japan next year to mark the 250th anniversary of Mozart's birth.