Missa De Profundis (1978) for 7-part chorus (SSATTBB) was written to be performed by a professional choir with at least three singers to a part. It is written to follow the a cappella tradition of the great Medieval-Renaissance period masses, each of the movements able to be used separately within the context of the Mass (albeit as performed by professional vocalists). The title "De Profundis" (Out of the Depths) comes from Psalm 129 (130), that psalm also set within the composition for solo bass and solo tenor. The writing of the Mass was begun just after Steven married in January, 1977, written during a time of religious conversion and at the birth of his first son, and completed after Steven entered the Catholic Church.

The Gloria and the setting of Psalm 129 (130) for which the Mass was named can be found below: