(Latin for 'Let us bless the Lord') is a closing salutation that was formerly used in the Latin Mass instead of the in Masses which lack the Gloria (i.e., Masses of the season during Advent, Septuagesima, Lent, and Passiontide; ferial Masses at which the Mass of the preceding Sunday was repeated, except in Eastertide; most votive Masses). The response, said afterwards, is ('Thanks be to God'). It is also sung as a versicle at the end of all Offices. The continues to be used in the Mass of the Lutheran Churches and in the Divine Office.
History and liturgical use
Apparently the chant was unknown in Rome before about AD 1000, and may have originated in the Gallican liturgy. In modern chantbooks, the music given for the chant is exactly the same as for the , but it is not known how much that was true in the medieval period as well.Hoppin, Richard. Medieval Music. New York: Norton, 1977. Page 142.
The text was frequently troped, especially by adding text between the two words, or using the melody as the for an . The use of this chant as a tenor was common in the St. Martial and Notre Dame schools of polyphony, including a dozen settings in the .
During the liturgical reforms of Pope Pius XII (1939–1958) and Pope John XXIII (1958–1963) the use of the was much restricted. By 1963, it was only recited or chanted when an exposition immediately follows the Mass (, 120). It is rarely heard in Anglo-Saxon countries, processions being rarities there. It is still however, used in the Divine Office.
The Lutheran Churches continue to use it in the Divine Office and at the end of the Mass (Divine Service).
Notes