A Unified Mass.

Sometime before 1365 the French poet and cleric Guillaume de Machaut composed a new work including the five sections of the Mass Ordinary—

Kyrie, Gloria, Credo, Sanctus, Agnus—plus the dismissal, the Ite Missa Est ("Go, the Mass is done"). As a point of unification, the composer selected relevant chants for each section as the borrowed tenor of each movement (that is, a Kyrie chant for his Kyrie, and so on). Each of these came from chants that were assigned for feasts in honor of the Blessed Virgin. In doing this he created the earliest unified set of Mass Ordinary movements. What is unusual about this concept...