ABSTRACT
This chapter examines a third kind of evidence: some manuscripts, dating from the tenth century and later, contain eighth-mode tracts other than those in the core repertory. Non-standard eighth-mode tracts appear only in manuscripts from certain areas, chiefly Aquitaine, Benevento, and Italy. Some chants appear only in one of these regions; some are common to two or more. The idea that a cantor might consciously write an eighth-mode tract incompatible with what he understood to be the construction of the genre appears to be foreign to medieval ecclesiastical culture, where stability and continuity were held in such high regard. In the core repertory, eighth-mode tracts are sung on the four Ember Saturdays of the liturgical year, and on some Sundays and some Saints days during Lent. The date of Easter varies by a factor of five weeks, between 22 March and 25 April and the moveable Feasts associated with Easter vary by the same factor.
