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. Based on freely written material probably composed by Ockeghem himself, and consisting entirely of mensuration canons,[1] it has been called "perhaps the most extraordinary contrapuntal achievement of the fifteenth century",[2] and was possibly the first multi-part work written with a unifying canonic principle for all its movements.[3][4]