Cantus firmus
A melody borrowed from one piece of music, and adapted as the basis for another piece by the addition of new, simultaneous voices.

[Example 1: Léonin: 2-voice organum: Alleluia Assumpta est Maria (opening)]

A cantus firmus is a melody borrowed from one piece of music, that is adapted as the basis for another piece by the addition of new, simultaneous voices. The result is polyphony. The source of the cantus firmus might be another work of the same composer, a different composer's work, a piece of anonymous Gregorian chant, or a popular tune.

The cantus firmus technique of composition began with the earliest forms of European polyphony and remained popular through the Renaissance, and is found most commonly in motets and in sections of the Mass. In the piece that you heard at the beginning, probably written by the medieval composer Léonin around 1180 at the Cathedral of Notre Dame in Paris, the borrowed melody is a monophonic Gregorian chant with the text "Alleluia." This is the original chant melody, sung by a group of men and boys:

[Example 2: Alleluia Assumpta est Maria: plainchant]

In the new composition, the chant melody appears in the lowest voice, in long, slowly moving notes while the newly composed upper voice moves more quickly above it. The voices are singing the same text, "Alleluia."

[Example 3, Léonin: Alleluia Assumpta est Maria (opening)]

Fig 1: chart depicting "layered" quality of cantus firmus composition

This basic arrangement is typical of many cantus firmus compositions: the borrowed melody provides a foundation for the composer, and the new polyphonic composition is layered on top like a multi-tiered cake. The voice carrying the borrowed melody usually sounds like the lowest or next-to-lowest part, and is called the tenor. In fact, the medieval or Renaissance composer would not have used the word "cantus firmus" at all; he would have said, simply, "tenor" and might have indicated in his composition where the tenor melody came from, if it was borrowed from another source.

Fig 2: "Armed man" illustration

In Léonin's piece, as we've heard, the borrowed source and the newly composed music share the same text and serve the same purpose in religious services: the new composition is a more complex version of the old chant. Often, though, the cantus firmus is borrowed from music that seems to have little or nothing to do with the purpose of the new composition. For example, a composer might take a popular tune and adapt it for a Mass. This is what happened in the case of a very famous Renaissance popular song, entitled "The Armed Man," whose text probably refers to one of the crusades against the Turks.

This simple tune was adopted by many composers, including the Renaissance composer Josquin des Pres [1440-1521], as the basis for polyphonic Masses. Here's the original tune:

[Example 4: L'Homme armé popular song: CD 653]

When Josquin borrows the tune for his new four-voice composition, he adapts it to fit the words of the Mass, rather than quoting both melody and text. And typical of Renaissance composers, the borrowed melody is not limited to the tenor voice. The tenor still presents the melody in its entirety as a true cantus firmus. But fragments of the melody spread into some of the other voices. This means that the cantus firmus becomes a very audible part of the listener's experience of the piece rather than a partially buried foundation -- very different from the medieval use of cantus firmus that you heard in the piece by Léonin.

In this section of a Mass Josquin wrote based on the "Armed Man" tune, listen carefully for the interval that begins the original tune: it is a perfect fourth:

[Example 5: upward 4th; first phrase of tune]

Fig 3: L'homme armé song, first seven notes

You probably won't be able to hear the original tune throughout Josquin's composition, because he shapes it to his artistic purposes for the Mass. But pay particular attention to the beginnings of phrases in the three highest vocal parts. There, you should be reminded of the original tune.

[Example 6: Josquin: Missa L'homme arme sexti toni: Agnus Dei: CD 653]

For the Renaissance or medieval composer, the apparent contradiction between the secular source material and the sacred final product did not necessarily pose a problem. Instead, it provided a means for the composer to show his skill in a manner that listeners could understand, since they were familiar with the borrowed melodies. In a way, cantus firmus composition works like "sampling" does today in popular music -- the cantus firmus provides the familiar hook that the audience already knows, and gives the listener some feeling that he or she "understands" the composer's work.

Summary:

• A cantus firmus is a melody borrowed from one musical source and adapted as the basis for a new polyponic composition, usually a motet, or a section of the Mass.
• Cantus firmus compositions were common in the medieval and Renaissance periods.
• The original source melody can be sacred or secular, with a known or unknown composer.
• The original source's text may or may not be related to the new composition's text.

Copyright © Columbia University, Visual & Sound Materials from the Gabe M. Wiener Music & Arts Library of Columbia University
Cantus Firmus written by: Annalisa Poirel Recording & Mixing: Terry Pender & Bradford Garton	Narration: Annalisa Poirel Technology & Design: Maurice Matiz