You’ve already studied the compositional technique known as cantus firmus, in which a new composition is built around a pre-exisiting melody. This technique continued into the middle of the Renaissance period. Josquin des Prez certainly used cantus firms in many of his works, but by Josquin’s time a new compositional technique, imitation, was becoming more popular among composers. Josquin’s own use of imitative counterpoint represents a high point in Renaissance polyphony. Read the first three paragraphs of this webpage for an introduction to imitative composition.