The Magnus Liber or Magnus Liber Organi contained a repertory of medieval music known as organum in use by the Parisian School of Notre Dame around the turn of the 12th & 13th centuries and is known from references to a "magnum volumen" by Johannes de Garlandia and to a "Magnus liber organi de graduali et antiphonario pro servitio divino" by the Englishmusic theorist known simply as Anonymous IV. Today it is known only from later manuscripts containing pieces named in Anonymous IV's description.
History
Although little is known of the provenance of the Magnus liber organi, it is considered most likely to have originated in Paris, and is known today by only a few surviving manuscripts and fragments, although there are records of at least seventeen lost versions.. The Liber is supposed to have been created by Léonin and revised by Pérotin and contained compositions attributed to each. Today its contents can be inferred from the 3 surviving major manuscripts. The most complete is commonly known as F, which first appeared in the library of Piero de' Medici by 1456. Of the two others, referred to as W1 & W2, both in the Herzog August Bibliothek, the first is thought to have originated in the cathedral priory of St Andrews, Scotland. The Ma fragment is, believed to be originally from Toledo. Catalogues referring to other lost copies attest to the wide diffusion through Western Europe of the repertoire later called ars antiqua. Between all the sources, some 100 different chants in two-part settings can be found. The music from the Liber has been published in modern times by William Waite, Hans Tischler and by Edward Roesner.
Music at Notre-Dame
The early music repertoire of repertory of Notre Dame cathedral represents one of the highlights of Western culture, coinciding with the architectural innovation that produced the structure itself, from the beginning of its construction in 1163. A handful of surviving manuscripts demonstrate the evolution of polyphonic elaboration of the liturgical plainchant that was used at the cathedral every day throughout the year. While the concept of combining voices in harmony to enrich plainsong chant, was not new, there lacked the musical theory to enable the rational construction of such pieces. The innovations at Notre Dame consisted of patterns of short and long musical notes and the system of musical notation for directing the duration of the notes in writing. This is attributed to Léonin, who is considered to have been a distinguished poet, scholar, musician and cathedral administrator. The Magnus Liber represents a step in the evolution of Western music between plainchant and the intricate polyphony of the later 13th and 14th centuries. The music of the Magnus Liber displays a connection to the emerging Gothic style of architecture; just as ornate cathedrals were built to house holy relics, organa were written to elaborate Gregorian chant, which too was considered holy. One voice sang the notes of the Gregorian chant elongated to enormous length ; this voice, known as the vox principalis, held the chant, although the words were obscured by the length of notes. One, two, or three voices, known as the vox organalis were notated above it with quicker lines moving and weaving together. The evolution from a single line of music to one where multiple lines all had the same weight moved through the writing of organa. The practice of keeping a slow moving "tenor" line continued into secular music, and the words of the original chant survived in some cases, as well. One of the most common types of organa in the Magnus Liber is the clausula, which are sections of polyphony that can be substituted into longer organa. The extant manuscripts provide a number of notational challenges to modern practice, since they contain only the polyphonic elements, from which the chant has to be inferred. The music of the Magnus Liber was used in the liturgy of the church throughout the feasts of the church year. The text contains only the polyphonic lines and the notation is not exact, as barlines were still several centuries from invention. The chant was added to the notated music, and it was up to the performers to fit the disparate lines together into a coherent whole. But the fact that the music was even written down is a fairly new development in the history of Western music.
