This chapter is an encyclopedia of the letter "O" covering the political, intellectual, literary, and musical history of the France from the early fifth to the late fifteenth century. The number of O antiphons grew to as many as twelve in some sources, with the addition of other texts to the original seven. The Occitan language developed its distinctive features from around the 5th to the 8th century. Johannes Ockeghem's personal appearance and manner, as well as his musicianship, were often praised by his contemporaries. William of Ockham was principally a theologian, vigorously exploring the philosophical limits of each epistemological, logical, or metaphysical issue, often to see more clearly the theological application. Under Odilo, Cluny reformed a number of monasteries to a regular life, especially in Burgundy. As abbot, Odo took over the direction of eleven houses, most located some distance from Cluny.