Walter Odington, a Benedictine monk at the abbey of Evesham, wrote this treatise in the late-thirteenth or early-fourteenth century, and it continued to appear in manuscripts until the end of the fifteenth century. Divided in six parts, it includes a tonary in part 5, which has close similarities with the Sarum Tonale. He addresses the differentiae of each mode in turn, and defines the types of antiphon beginnings appropriate to each differentia. This treatise is not translated and remains in its original Latin.
Scriptorum de musica medii aevi nova series a Gerbertina altera, 4 vols., ed. Edmond de Coussemaker (Paris: Durand, 1864-76; reprint ed., Hildesheim: Olms, 1963), 1:182–250.