Gregorian chant is the central tradition of Western plainchant, a form of monophonic, unaccompanied sacred song of the western Roman Catholic Church. Gregorian chant developed mainly in western and central Europe during the 9th and 10th centuries, with later additions and redactions. Although popular legend credits Pope St. Gregory the Great with inventing Gregorian chant, scholars believe that it arose from a later Carolingian synthesis of Roman chant and Gallican chant.