Which of these best describe Dufay’s use of “Cantus firmus”
A. He would take old Gregorian chants and rewrite them in retrograde (that is, the piece was written in reverse).
B. He would take old Gregorian chants and write them an octave higher so that women could sing them more easily
C. He would take an older Gregorian chant and use this as the basis for the thermatic material or bass voice in a new polyphonic work
D. He would take old Gregorian chants and rewrite the melody for lute