A good indication of the Renaissance mind-set, in the early fifteenth century, was a new way of treating plainchant in polyphonic compositions. Medieval composers writing organum or isorhythmic motets seem to have felt that so long as they used a traditional plainchant, there was nothing wrong with distorting it. They lengthened its notes enormously underneath the added counterpoints. They recast the meterless chant into fixed, arbitrary rhythms.

Renaissance composers no longer felt obliged always to use plainchants; but when they did, they tended to treat them as melodies to listen to, not as scaffolding for polyphonic structures. They embellished chants with extra notes, set them in graceful rhythms, and smoothed out passages that struck them as awkward or old-fashioned. This procedure is known as paraphrase.

Renaissance composers using paraphrase emphasized the sonorous, sensuous aspect of the chant rather than its function as structure and control — its authoritarian function, one might say. (Sonority means either tone color or, more loosely, rich tone color.) A new sensitivity to sonority and melody was one of the first signs of Renaissance attitudes toward music.

Having transformed plainchants into modern melodies with a more attractive profile, composers put them not at the bottom of the polyphony but on top, in the soprano, where they could be heard most clearly.