Mozart had barely turned twelve when he composed and conducted his Missa solemnis in C minor, K.139, to inaugurate a new orphanage on Vienna’s Rennweg in 1768.

This astonishing early work adheres to the form of aNeapolitan cantata mass, in which the separate movements (“Gloria”, “Credo” etc.) are themselves made up of self-contained choruses, ariosos and ensembles.

This frequently heard Mass is characterized by a sharp contrastbetween its cheerful underlying C major mood and gloomy drama...