A musical Mass for the dead, celebrated in the Roman Catholic Church. It receives its name from the first word of the Introit. Requiem aeternam dona eis Domine (“Give them eternal rest, O Lord”). This introit is also often recited by itself as a prayer for the departed soul. Although the requiem was intended to be sung only at funerals, at anniversary memorials for the departed, and on All Souls' Day (1 November), due to its limited use it became a concert form. The opening sections of the requiem uses traditional Gregorian chant melodies, and by the eighteenth century orchestral accompaniment had gained importance. Guiseppe Verdi's Requiem in memory of Italian novelist A. Manzoni is probably the best known.