Cantus firmus

In music, a cantus firmus ("fixed song") is a pre-existing melody forming the basis of a polyphonic composition.

The plural of this Latin term is , though the corrupt form canti firmi (resulting from the treatment of cantus as a second- rather than a fourth-declension noun) is also attested. The Italian is often used instead: (and the plural in Italian is ).

History

The earliest polyphonic compositions almost always involved a cantus firmus, typically a Gregorian chant, although the term itself was not used until the 14th century. The earliest surviving polyphonic compositions, in the Musica enchiriadis (around 900 AD), contain the chant in the top voice, and the newly-composed part underneath; however this usage changed around 1100, after which the cantus firmus typically appeared in the lowest-sounding voice. Later, the cantus firmus appeared in the tenor voice (from the Latin verb 'tenere', to hold), singing notes of longer duration, around which more florid lines, instrumental and/or vocal, were composed.

Composition using a cantus firmus continued to be the norm through the 13th century: almost all of the music of the St. Martial and Notre Dame schools uses a cantus firmus, as well as most 13th century motets. Many of these motets were written in several languages, with the cantus firmus in the lowest voice; the lyrics of love poems might be sung in the vernacular above sacred Latin texts in the...
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