Missa In C Major K.258

The dating “nel mese Decembre 1776” on the autograph of the Missa K. 258 is not authentic; it was most likely written towards 1775/76. On the autograph, Leopold Mozart inscribed the title Missa, but at the incipit on the oldcover of the autograph collection, he wrote Missa brevis. This points to the lack of standardization and uncertainty of the nomenclature. Although the work is written in the brevis form, it calls for additional instruments besides the usual church trio, which assigns it to the genre of the brevis et solemnis mass. Mozart added two oboes, whose parts he wrote out himself and which are enclosed together with the primary copy. The two oboe partsseemto have been unavailable to any copyists.