Cantus firmus

A pre-existing melody used as the structural basis for a polyphonic composition, often presented in long notes beneath or within newly written voices.

Polyphony: Music in which two or more independent melodic lines sound simultaneously. A cantus firmus provides one line around which other independent melodies are composed.
Gregorian chant: The central tradition of Western plainchant associated with the Roman Catholic Church. Its melodies supplied many of the borrowed tunes in medieval and Renaissance works.
Cantus-firmus Mass: A Mass setting whose movements use one borrowed melody as a recurring structural basis. The cantus firmus unifies movements while composers vary its placement and treatment.
Johannes Ockeghem: A fifteenth-century Franco-Flemish composer known for complex Masses and contrapuntal writing. His Masses show the cantus firmus supporting elaborate canonic structures.
Counterpoint: The composition and combination of independent melodic lines in music. Cantus-firmus writing is a foundational way to organize contrapuntal voices.
Organum: Medieval polyphony in which one or more voices are added to a chant melody. Early organum often kept chant as a sustained structural line beneath added voices.
Motet: A polyphonic vocal composition, usually sacred, with one or more texted parts. Renaissance motets often build their polyphony around a chant cantus firmus.
Josquin des Prez: A Franco-Flemish composer of the late fifteenth and early sixteenth centuries. He made borrowed melodies the basis for Masses with varied and expressive treatment.
Note values: The relative durations assigned to written musical notes. Long note values distinguish the structural melody from its more active surrounding parts.
Notre-Dame school: A group of composers associated with the development of polyphony in twelfth- and thirteenth-century Paris. Its practice of placing measured lines above sustained chant helped establish cantus-firmus technique.

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