Medieval Poliphony

The greatest musical achievement in the history of music, occurred during the Middle Ages, was the coming of polyphony. Polyphony requires two or more vocal parts sung simultaneously, each with its own individual melodic importance. Music in the Middle Ages had began as monophonic chant, then around 1000 A.D., new types of polyphony developed and gradually  expanded in rhythm, harmony and texture until reaching an extremely complex style in the late 1300s. One of the most ancient vocal forms of Medieval Ages was called plainchant or plainsong, the Gregorian chant. Polyphony emerged in the 8th or 9th century and, in Musica Enchiriadis ("Musical Handbook"), attributed to the theoritician Hucbald, it is described as derived from the early elementary form of "parallel organum". It was a chant with a strict parallel progression of fourth or fifth. The two voices start in unison while the vox organalis climbs to the interval of fourth or fifth, returning at the ends of the phrase to the unison. The principal voice appeared above the tenor, the organal voice. The improvisation over a gregorian monody to embellish it was a common practice until the 15th century. 

    Florid  or melismatic organum is composed of unmeasured melismas over long tenor notes. It consented the use of fourths, fifths as well as thirds and sixths. The long-held notes were in the lower part, whereas,  in the upper parts were the melismas. 

Paris became the main center in the production of organa, thanks to the School of Notre Dame (12th and 13th centuries). The most important composers of organa were Léonin, and Perotin. The latter is believed to have added a third voice called triplum and sometimes even a fourth, the quadruplum. 

        CONDUCTUS: Originally, the conductus was a monodical processional chant with a stanzaic structure, used in religious rituals, and for civil occasions. Texs were shaped on circumstances. The main voice (vox principalis)is in the lower part, while the duplum and/or triplum sung in the discantus' style.

XIVth century MOTET: it was a 2, 3 or 4 voices compositions, built on a lythurgical melody (the tenor being on the lower part), the cantus firmus, and tuned on different texts. 

FLEMISH MUSIC

The Flemish composers and musicians were originary of Flanders and the North of France. They gave an important contribution to 15th century  poliphony. Some of the most important names were, G. Binchois, G. Dufay, J. Ockeghem, J. Obrecht, J. Desprès. They improved the art of poliphony thanks to a complex counterpointal imitative structure of music, which established new rules for music composition.