- Date: 12th century
- Composer: Léonin
- Period: Medieval (1-1449)
Review
Literally "big book," the term Magnus Liber refers generally to a body of compositions associated with the establishment of the Cathedral of Notre Dame in the late twelfth century. The Magnus Liber is not a particular book, however, but rather a large repertory of compositions found in a number of medieval manuscripts, all of them supposedly traceable to an original collection created by the composers at Notre Dame. The most prominent of these, Léonin and Pérotin, are generally credited with developing the techniques of composition that would eventually give rise to what is perhaps the most prominent feature of Western art music: the interaction of multiple voices to create harmonies, or polyphony. The music associated with the Magnus Liber is thus, according to one authoritative scholar, "perhaps the greatest single achievement in medieval music."Although some mention of polyphony appears in earlier writings, such as those of Guido of Arezzo (eleventh century), the music of the Magnus Liber represents the establishment of a large body of polyphonic pieces used regularly in liturgical or paraliturgical settings. Though the various contributions of the authors of the music in the Magnus Liber repertory is not clear (Léonin and Pérotin were probably joined by several others in the preparation of the original collection), Léonin is generally known (and described by later writers, such as Anonymous 4) for his mastery of the organum. This initial type of polyphony is comprised of two voices, one singing the traditional plainchant line of the liturgy, the other singing the newly composed "organal" line. Two types of two-voice organum appear in the Magnus Liber. The first, often referred to as "organum purum," is characterized by long melismas or melodic flourishes in the organal voice, sung above long-sustained notes in the plainchant voice, or tenor (from the Latin "tenere," meaning "to hold"). The other type of organum is known as "discant," and is characterized by a tenor voice moving through the original plainchant melody at a much quicker pace, nearly equal to that of the tenor voice; this would usually be applied to more florid passages of the original chant. Such coordination required new developments in rhythm, which also set apart the Notre Dame School as particularly important in the development of Western music.
Organa were composed for the responsorial chants of the liturgy (that is, those chants in which a soloist alternates with a choir, such as the Gradual), and were applied only to those parts of the chant originally sung by a soloist. Thus in practice, singers of Léonin's music would perform a Gradual by singing the soloist's part in two-voice organum, alternating with a choir singing their passages in unison. Pérotin is recognized for expanding the practice of organum to three or even four voices, and also helping develop extended discant passages into independent compositions called "clausulas." Eventually, the added music of the clausula was given additional text, which marked the creation of the most important musical development of the subsequent century, the motet. ~ Jeremy Grimshaw, All Music Guide
