The middle Ages in music began in 313, when the Roman emperor Constantine the Great embraced Christianity, emerging form underground, the church immediately established a schola cantorum in Rome for the training of musicians, Church music then consisted, as it had since pre-Cristian Judaism, of Plainsong, liturgical texts chanted to flowing melodies without measured rhythm. The Roman liturgy became standard in Western Christianity due primarily to the effort of Gregory I, pope from 590 to 604. The body of plainsong is known as Gregorian chant in his honor, although it seems not to have reached its final from until the 8th century.
Expansion of Liturgy
Classical music theory, transmitted (6th century) by Boethius and studied by all aspirants to the clergy, equipped medieval musicians to use tropes, textual or musical additions, to extend the received texts and melodies of the plainsong Mass. These plainsong additions, newly composed to poetic texts, were inserted between or even within the regular chants. Tropes could become quite lengthy, even theoretical.
The sequence originally a mere tag to the Alleluia of the Mass, began around the same time and in the same way as the trope, but it eventually detached itself from particular chants to become independent composition.
Development of Polyphony
Simultaneous with the ration by polyphony (more than one melodic line sounding simultaneously). This technique began modestly enough with the parallel organum of the 9 thin parallel. Eventually, voices moved in dependently of the melody, and the original chant, the cantus firmus or tenorfantastic' decorations. Leading schools in this florid organum were located at St. Martial in LimogesParis (1175-1220), especially under the latter's two great masters, Leonin and Perotin. (literally, holder), had to be slowed down to accommodate the other voices ' (1100-50) and Notre Dame in century, in which two singers began on different pithches, separated by the musical interval of a fourth of fifth, and sang the same melody.