C 1.12, was probably composed by Wolfgang Amadeus Mozart shortly after returning to Salzburg, in March 1773, from his third trip to Italy.

[2] Ludwig von Köchel, in the first edition of his catalog of Mozart's music, thought the Mass roughly contemporary with Lucio Silla and "Exsultate, jubilate" (1772-1773).

Alfred Einstein thought its original composition to be closer to that of the sixth Serenade (1776) with his revision of Köchel's catalog in 1937.

[2] The earliest surviving score and parts, found in a cloister in Augsburg, Germany, were prepared by a copyist, with completions and corrections in Mozart's hand.

[2] The mass is scored for soloists, choir, strings and organ, the latter playing from figured bass.