(Leoninus; fl. 1154-ca. 1201). Anonymous 4’s epithet optimus organista (“the best singer/improviser/ composer/compiler/notator of organum”) assured Léonin a significant place in music history long before any convincing identification of the person was suggested. Since he was responsible for the new polyphonic repertory of the cathedral of Notre-Dame in Paris in the decades after its founding in the 1160s, his place was evidently among the dignitaries of its ecclesiastical hierarchy, but the familiar use of the Latin diminutive of his name, as “Magister Leoninus,” in the theoretical treatise of Anonymous 4—the only source for information on his considerable musical achievement—long seemed to belie this. Anonymous 4 credited Léonin with the Magnus liber organi de gradali et antifonario some one hundred years after its compilation, a fact that recommends cautious use of his testimony and the need for independent verification. Three major manuscript sources (W1, F, and W2) confirm a repertory of organum that fits Anonymous 4’s description of a Magnus liber organi, and the melodies of the plainchant that form the basis of that organum match notated plainchant sources used at Notre-Dame.
Still, this does not clarify what Léonin’s role may have been in making such a book. Optimus organista suggests a youthful man in full voice, while the diminutive implies a beloved elder whose practical contributions may have been overshadowed by his administrative usefulness—two very different “portraits” of the individual. It may not have been so much by his initiative as by his approval that modal rhythm became the primary innovation of the Notre-Dame School, and there is no certain evidence that such rhythm was subject to systematic theoretical or notational principles during his lifetime.
Archival evidence only recently brought to light establishes a probable identity for Anonymous 4’s Magister Leoninus as Magister Leoninus presbyter, a canon active in the affairs of the cathedral during the late 12th century and a Latin poet whose hexametric Old Testament commentary, Hystorie sacre gestas ab origine mundi, was long praised after his death. There is, however, no document, except possibly the treatise of Anonymous 4, to substantiate the involvement of Leoninus presbyter with music at all, a striking omission given the significance of the Magnus liber organi and the stature of the poet. Thus, while the search for independent, corroborating evidence continues, the hypothesis that Léonin, known also as Magister Leoninus presbyter, was responsible for the vanguard of virtually a new era in music with the Magnus liber organi should remain compelling.
