(Lat.) : A melody from some other work borrowed to serve as the basis for a new polyphonic composition. Josquin's Déploration sur la mort de Joh. Ockeghem incorporates a plainchant Requiem in aeternam as cantus firmus (in the tenor voice). In the Renaissance, a great number of polyphonic masses were based on the famous song "L'Homme armé" (The Armed Man) as cantus firmus. Vestiges of the practice can be seen in the 19th-century fondness for weaving, for example, the Gregorian Dies irae into macabre compositions--as in the last movement of Berlioz's Symphonie fantastique.