Leonin was an important theorist, composer and compiler of the Middle Ages. Much of the information available concerning Leonin comes from the writings of Anonymous IV who lived a full century after Leonin. Data is mixed with legend and some think that Leonin may in fact be primarily a legendary figure. His major contribution to musical history was the "Magnus Liber" which was the collection of medieval polyphonic pieces for the liturgical part of the service. Specifically the "Magnus Liber" was written for settings in Notre Dame Cathedral, Paris; accordingly, Leonin is ascribed as being a predominant figure in the musical life of the Cathedral. The "Magnus Liber" contains polyphonic settings for two voices of the solo portions of graduals, alleluias, and responsories for the major feasts of the entire liturgical calendar. Up until the creation of the "Magnus Liber" polyphony had been carried out through an improvisatory style; the work structured the role of the singers in an appealingly aesthetic manner. The strains were melismatic with a smooth and lilting flow illustrated by gentle curves in the shape of the melodic line. Leonin is thought to have invented notational rhythmic devices but this is highly contested as being anachronistic. Modal rhythms were assumed to have been Leonin's concern but whether he intended this to be the case is in question. A discant is now present in the complete work but this too is questionably Leonin's device. When employed the two voices move together and in similar meters. Otherwise, two voices, as in the case of the traditional polyphony, were often scored note-against-note. ~ Keith Johnson, Rovi