The development of the motet from the late 14th century to the 15th century

Quam pulchra es ~ John Dunstable

If  Quam pulchra es had been written a century earlier, as a mostly homorhytmic setting of a Latin text, it could be classified as a cantilena, but in the fifteenth century it would be called a motet. This term, coined in the 13th century for pieces that added text to the upper part of a discant clausula, gradually broadened in meaning to include any work with texted upper voices above a cantus firmus with both sacred or secular text. By the early fifteenth century, the isorhythmic motet was an antiquated form, used for only the most formal of occasions, and by 1450 it fell out of fashion. Meanwhile, the term motet was applied to settings of liturgical texts in the newer musical styles of the time, whether or not a chant melody was used. The term came to designate almost any polyphonic composition on a Latin text, including settings of texts from the Mass Proper and the Office. It was even used for settings of Mass Ordinary texts before the mass cycle became its own genre around the mid-fifteenth century.