Note 52 — Chapter III · THE LITURGY OF THE CATHOLIC CHURCH

The musical composition commonly called a Mass—such, for instance as the Imperial Mass of Haydn, the Mass in C by Beethoven, the St. Cecilia Mass by Gounod—is a musical setting of those portions of the office of the Mass that are invariable and that are sang by a choir. These portions are the Kyrie, Gloria, Credo, Sanctus and Benedictus, and Agnus Dei. The musical composition called Requiem, or Mass for the Dead, consists of the Introit—Requiem aeternam and Te decet hymnus, Kyrie eleison, Dies Irae, Offertory (Domine Jesu Christe), Communion—Lux aeterna, and sometimes with the addition of Libera me Domine. These choral Masses must always be distinguished from the larger office of the Mass of which they form a part.