Machaut's "Messe de Notre Dame" stands as an enduring monument of medieval musical art. As such it is one of the most widely studied and performed works of music written before 1600. The Mass itself, however, is surrounded by uncertainty; its date of composition is unknown, its purpose is unclear, and its construction yields much ambiguity. Daniel Leech-Wilkinson has prepared a modern performing edition of this work, published by OUP's music department. This companion volume defines his editorial methods in the context of the minefield of controversies surrounding the principles of editing music of this period, and indeed of the many different interpretations of the compositional structure and function of the music. Relating the Mass to other works of the period, he provides the student and performer with a guide to its intricacies.