Gregorian chant is the best-known repertory of plainchant, a form of monophonic, unaccompanied sacred song, which was developed in the Catholic Church, mainly in western and central Europe during the period 800-1000, with later additions and redactions. It is believed to have arisen from a Carolingian synthesis of Roman chant and Gallican chant, but came to be associated with Pope St. Gregory the Great, who was believed in legend to have composed the chant guided by divine inspiration.