The Great Mass in Cm, K. 427/417a, is a work by Wolfgang Amadeus Mozart, written in 1782-3 in Vienna. The work is incomplete, missing all of the Credo following the aria "Et incarnatus est" (the orchestration of the Credo is also incomplete) and all of the Agnus Dei. The Sanctus is partially lost and requires editorial reconstruction. There is a good deal of speculation concerning why the work was left unfinished. Given the absolute necessity of a complete text for liturgical use, it is likely that Mozart spliced in movements from his earlier Masses for the premiere, although Richard Maunder has noted that the surviving parts (including an organ part) contain only the completed movements. For purposes of modern performances, the editions and completions available are those by H. C. Robbins Landon (Eulenburg), Helmut Eder (Bärenreiter), Richard Maunder (Oxford University Press), Philip Wilby (Novello), Robert Levin (Carus-Verlag) and Benjamin-Gunnar Cohrs (Musikproduktion Höflich). Robert Xavier Rodriguez has also completed the Agnus Dei. The work calls for a large orchestra, two choirs and STAB soloists.
