Missa prolationum

The Missa prolationum is a musical setting of the Ordinary of the Mass by Johannes Ockeghem, dating from the second half of the 15th century.

The interval separating the two voices in each canon grows successively in each consecutive movement, beginning at the unison, proceeding to the second, then the third, and so forth, reaching the octave at the "Osanna" section in the Sanctus.

What has so astonished musicians and listeners from Ockeghem's age to the present day is that he was able to accomplish this extraordinarily difficult feat.

[5] Ockeghem was the first composer of canons at the second, third, sixth, and seventh (the "imperfect" intervals), and the Missa prolationum may have been the first work to employ them.

In Ockeghem's time, composers usually built masses on preexisting tunes such as Gregorian chant or even popular songs.