The four-part conductus Vetus abit littera (The old order passes away) is only one of three known conducti composed in four parts. It is found in the largest extant manuscript containing music from the so-called "Notre Dame School" of polyphony, held in the Medici Library in Florence under the shelfmark of Mediceo-Laurenziana Pluteo 29.1; scholars commonly refer to this source as "F1." With its dense, closely voiced, and rather dissonant harmony, some scholars have suggested that Vetus abit littera is the work of medieval Notre Dame composer Pérotin. The source, however, is anonymous and this title is not mentioned in the short list of pieces attributed to Pérotin by the medieval scribe known as Anonymous 4, whose famous treatise also originates with F1. The text, intended for use at Christmastime, is a non-biblical medieval poem that celebrates the new covenant with the Lord through Christ. It begins, "The old order passes away/the rites of the ancients are gone/Through childbirth the virgin/has given us a new son." ~ Uncle Dave Lewis, All Music Guide
