Mass No.13 in C major, KV 262/246a ""Missa longa""

The mass is classed as a missa longa due to its length. However, due to its lack of extended writing for the solo parts, it has also been categorised as a missa brevis. The occasion the mass was composed for remains debatable. It may have been composed at the Archbishop Colloredo's request for a special occasion at the Salzburg Cathedral, or at the directive of a different priest – Colloredo's preference for brief settings makes it unlikely that he would have approved of the missa longa. Alternatively, it may have been composed for performance at St Peter's Church.