Most music historians would probably have little trouble accounting for the normative formal principles of a fourteenth-century rondeau or isorhythmic motet. A topic that has occasioned much less notice, however, is the question of formal articulation in the parallel corpus of liturgical works produced in no small quantity through to the end of the century, from the Tournai Mass to the earliest layer of works contained in fifteenth-century sources such as Bologna Q 15. What relatively little the scholarly literature offers on this subject has tended to portray the composition of masses either as being wholly derivative of secular forms (the typical view), or at best as reflecting some sort of murky attempt at through-composition.