The principal method for constructing large-scale pieces during the age of Dufay and Josquin was cantus firmus technique, whereby a preexisting tune placed in the tenor (by then that part just above the bass) would serve as the scaffolding for the entire piece. During the 16th century treatment of the cantus firmus became increasingly loose. Instead of quoting a melody literally, composers now more likely than not would paraphrase it, changing rhythms and adding or subtracting notes, in effect creating an entirely new melody. Nor need the cantus firmus be confined to a single voice-it might "rnigrate" from the tenor to another voice part or even appear in two or more parts simultaneously. This latter procedure gives rise to still another: to base a work not on a single melodic fine but on two or more parts taken from another piece. Though this new practice, termed parody, is a logical extension of the old, it actually introduces a revolutionary concept. Both cantus firmus and paraphrase composition draw from a monophonic model; parody, on the other hand, depends on a polyphonic model. Parody should not be viewed in the derogatory sense of "to make fun of," but rather simply in the sense of "to derive from." Frequently composers would take the entire musical substance of a chanson, motet, mass, or madrigal and rework it to form a piece recognizably their own. As a rule, they transformed a relatively simpler design into one of greater complexity.
Parody technique, which became the standard means of Mass composition by 1540, strikingly reveals the liberal attitude taken by Renaissance composers toward preexisting music. No crime was attached to borrowing from a contemporary; indeed, this was a way of honoring him and at the same time showing off one's own ability by improving upon the work of another. Not until the 19th century did "originality" become the restrictive albatross it has remained for composers today.