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.
Beethoven called Mozart's Requiem "wild and terrible", and that's what we get in Harnoncourt's new recording. Ominous dread hangs from every note of the dark opening measures, the Rex tremendae and Confutatis are driven with terrifying strength, and the supplications of the Lacrimosa, with their weeping stabbings of the orchestra, are freighted with emotional power. The Tuba mirum duet of bass soloist and trombone has a beauty almost never achieved in other readings. Nor does Harnoncourt overstep the stylistic boundaries of this classical-era work; rather, the intensity is heightened for being in the idiom of its time.