"Allez regrets" is a chanson usually credited to Hayne van Ghizeghem. Together with the composer's "De tous biens plaine", this was one of the most famous chansons of the age, and was much used as a basis for variation and as a cantus firmus for mass settings.
Cholji, Irena. "Borrowed Music: Allez regrets and the Use of Pre-existent Material." In Companion to Medieval and Renaissance Music, ed. Tess Knighton and David Fallows, 165-76. New York: Schirmer Books, 1992. see for summary