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There is even more ingenuity in this work. The title, Mass of prolations, refers to the time signatures used in mensural notation, which was predominant from the 13th to the 17th centuries. There were four prolations, derived from four combinations of tempus and prolatio. The breve could be divided into two semibreves (tempus imperfectum) or three semibreves (tempus perfectum), and the semibreve could be divided into two minims (prolatio imperfecta) or three minims (prolatio perfecta). In modern notation, a whole note is normally divided only into two half notes, and a half note only into two quarter notes. Each of the four voices in the Mass sings a different meter, or prolation. If all of this sounds forbidding, we must remember that because of Ockeghem’s genius the result is of surpassing beauty, and it requires no effort of comprehension on the part of the listener.
Another freely composed Mass that demonstrates Ockeghem’s technique is the Missa Mi-Mi. It is generally considered that the name is derived from two notes that are sung at the beginning of the bass part in each movement. They comprise a falling fifth, e to A. In the system of Guido of Arezzo, e is mi in the natural hexachord, while A is mi in the soft hexachord. Guido described three six-note scales, or hexachords. The hard hexachord begins on G, requiring a B flat; the natural hexachord begins on C, omitting B entirely; and the soft hexachord begins on F, requiring a B natural.
More recently Leeman Perkins has asserted that the falling fifth cannot be the source of the title, for the A cannot belong to the soft hexachord. He states that the name is based on the repetition of e in the superius, or highest part.
Last year Gayle Kirkwood proposed that the Missa Mi-Mi is a musical witness to the mystical theology of Jean Charlier de Gerson, with Gerson’s understanding of Christ illustrated in the melodic and structural details of the Agnus Dei.
The third of these ingenious Masses is the Missa cuiusvis toni, the “Mass in whatever mode”, the least familiar of the three in performance and on records. Ockeghem wrote the parts without clefs; hence, depending on where the clefs are placed on the staff, the half-steps would occur in different places, and the music might be sung in different modes. In a recent edition of the Mass (1992), the entire work is printed four times, once in each of the medieval pairs of modes. According to the editor, George Houle, the Phrygian mode (modes 3 and 4) and the Mixolydian mode (modes 7 and 8) sound well, but the Dorian mode (1 and 2) and the Lydian mode (5 and 6) require so much musica ficta (accidentals added by the singers) that it is hard to imagine performers resourceful enough to sing them at sight.
After two previous recordings had omitted one or two movements, Siegfried Heinrich recorded the complete Mass, issued in 1979. On one side of the record the Mass is sung by solo voices in the Phrygian mode, and on the other side it is sung by a choir in the Mixolydian mode. The record is filled out with the Kyrie played in the Lydian mode and the Agnus Dei played in the Dorian mode. Clearly he took the same view toward the various modes as Houle does. The disc was a problem for all but experts, for the labels were reversed, confusing most listeners.
Peter Urquhart puts a different interpretation on “any mode”, since Glareanus suggests that “the tenor can begin on ut, re or mi”. Rather than choosing one of four medieval modes, Glareanus uses solmization to assign ut (do), re or mi to the first note of the Mass. This permits three different performances of the music, each of which is said to work satisfactorily (Houle would not agree that the mode on re, the Dorian, sounds well). Urquhart has recorded the Mass on ut, that is, in the Ionian mode, a mode that was unknown in the Middle Ages.
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