What the Meaning for cantus firmus?

Cantus firmus, Latin for "fixed song," refers to a pre-existing melody used as the foundational basis for a polyphonic composition. In the context of medieval and Renaissance music, it often served as a structural anchor around which other voices are harmonized or elaborated. This technique allowed composers to create intricate musical textures while maintaining a recognizable melodic line. Cantus firmus is significant in the development of Western music, particularly in the creation of sacred choral works.