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