First things first: if you're seeing a picture of this disc on the site of an online retailer, be aware that it contains the Mass in C minor, K. 427, not the "Mass in C," promised by the cover, which would more likely be the "Coronation" Mass in C major, K. 337. It is always a shame when designers are given power of diktat over content editors. The so-called "Great" Mass in C minor is one of Mozart's most ambitious and most problematical works. There was no known immediate stimulus for its composition. Did Mozart begin writing it out of one of his rare religious impulses, on the occasion of his marriage to his bride Constanze? Out of his growing devotion to Freemasonry? Was it his first major exercise in applying the lessons in Bach-style counterpoint he had been receiving at the intellectual salons of the Baron van Swieten in Vienna? Or was it meant as a showpiece for singer Constanze with its killer soprano arias? It was all of these things and none of them, for Mozart never finished the mass.