More than any others of the time, the works of Johannes Ockeghem are considered to have marked the summit of the entire development of polyphonic structures during the Middle Ages. His works, although few in number, are supreme examples of creative thought. An undisputed master of his musical materials, certain of his Masses are structured around his own reflections on the art of composition. This is the case with the Missa Mi-mi: its title comes from the initial motive in the bass line, this consisting of the notes E and A which, in the system of solmisation in use at that time, can be read as mi-mi. Together with a Gregorian proprium, it is integrated here into the Office for Maundy Thursday.