Verdi's Requiem, for orchestra, four soloists, and double choir, is a colossal setting of the Catholic mass. Now a standard of the choral repertoire, and operatic in its scale and grandeur, it may never have existed if not for the ill-fated collaboration by several Italian composers to honor the life of Rossini with a requiem in his honor. Verdi expanded his contribution to this project into the emotional and revered work we know today.