Octavio dei Petrucci, of Fossombrone, invented movable types for printing music in 1502, and obtained a patent for the exclusive use of the process for fifteen years in 1513. By that time the advance in the mastery of counterpoint had left Ockeghem somewhat out of fashion; and it is, therefore, not remarkable that Petrucci's earliest collections contain nothing by this master. Not till years after his death was any mass or motet of his given to the world. Then only one was printed entire. This was his "Missa cujusvis toni," which was plainly selected because of its science. Extracts from his "Missa Prolationum" were used in theoretical treatises; and, indeed, Ockeghem's music seems generally to have been cherished wholly on account of the technical instruction which might be derived from it. The list of his extant compositions, as given in Scribner's "Cyclopedia of Music," is as follows: "Missa cujusvis toni," in Liber XV., missarum (Petreius, Louvain, 1538); six motets and a sequence (Petrucci, Venice, 1503); an enigmatic canon in S. Heyden's "Ars Canendi" and in Glarean's "Dodekachordon"; fragments of "Missa prolationum" in Heyden's book and in Bellermann's "Kontrapunkt"; mass "De plus en plus," MS. in Pontifical Chapel, Rome; two masses, "Pour quelque peine" and "Ecce ancilla Domini," in the Brussels Library; motets in MS. in Rome, Florence and Dijon; six masses, an Ave and some motets in Van der Straeten; Kyrie and Christe, from "Missa cujusvis toni" in Rochlitz. This list is probably correct except the six motets and a sequence set down as published by Petrucci in 1503. Ambros, who is always trustworthy and who mentions all these works and also three songs ("D'ung aultre mer," "Aultre Venus" and "Rondo Royal") and a motet ("Alma redemptoris") in MS. at Florence, did not discover any publications by Petrucci. The enigmatical canon was solved by Kiesewetter, Burney, Hawkins and other historians; but the solution believed to be most nearly correct is that of the profound contrapuntist and excellent historian, Fétis. Glareanus (Dodekachordon, p. 454) speaks also of a motet for thirty-six voices. This was, no doubt, originally written for six or nine voices, the other parts being derived from them by canons. It is not certain, however, that Ockeghem ever wrote such a work. The "Missa cujusvis toni" ("A mass in any tone," or scale, as we should say now) may have been written as an exercise for the master's pupils, as some historians conjecture, but it seems more probable that it was a natural outgrowth of the puzzle-building spirit of the time and of Ockeghem's especial fondness for displays of musical ingenuity. The peculiarity of the mass is that it employs in a remarkable manner all the church modes or scales. It was sung in Munich many years after Ockeghem's death and a corrected copy of it is still preserved in the chapel.