A Requiem is a term usually used for the Catholic Mass for the Dead. The introit, or section of the service sung by the priest in approaching the altar, begins with the words “requiem æternam”. It is a request for perpetual peace and rest for the soul of the dead person for whom the Mass is celebrated. To invoke fitting solemnity, the joyful Gloria and Credo are omitted.
The wording is also slightly changed, and a Dies iræ is interpolated. This is a setting of a thirteenth century poem by Thomas of Celano. Its words recall the terrible day of wrath in store for the souls of the dead, from which Christ's sacrifice alone can save them. In musical settings, the Dies Irae is divided into several contrasting sections, one of which is the prayer Ingemisco tanquam reus.
Early plainsong Requiems exist. Later compositions include those by Palestrina, Berlioz, Verdi, Fauré, and Dvorak. Mozart's last work was an unfinished Requiem, composed on his own deathbed.
Giuseppe Verdi was to be one of several composers contributing different sections to a Requiem written on the death of Rossini in 1868. This collaborative work was never completed, but Verdi used the ideas he developed on this occasion for the magnificent Requiem first performed in 1874 after the death of the Italian novelist Manzoni.
