Mozart provided a steady output of Masses during his time at the court in Salzburg. The fine Missa brevis in G major was composed in 1768 when Mozart was just twelve years old. The theatrical and inventive 'Credo' Mass in C major, from 1776, is regarded as one of Mozart's finest achievements from this period. The profound key of D minor for the Missa brevis, K. 65 reflects it's use at a 40-hour vigil, while the affectionate nickname 'Spatzenmesse' ('Sparrow Mass') for the Missa brevis in C major refers to the chirping nature of the Sanctus.