(Latin; " fixed chant ")
Preexistent melody, such as a plainchant (see Gregorian chant ) excerpt, underlying a polyphonic musical composition (one consisting of several independent voices or parts).
In the 11th-and 12th-century organum , the tones of the plainchant melody for such words as "alleluia" and "amen" were held by one voice (the tenor), while another, more active, improvised line was added. Developments introduced by the Notre-Dame school of the late 12th and early 13th centuries included rhythmic patterning of the added voice and the addition of two or three voices. The composition of nonliturgical words for the added voice or voices in the 13th century resulted in the independent motet . Cantus firmus technique remained the basis of most composition of the 14th–15th centuries (though the "chant" was now often a secular melody) and remained important in the 16th-century mass . It was later codified in the pedagogical method called species counterpoint .