Organum

Organum is a kind of music developed in the Middle Ages and may be the first true polyphonic music. It begins as discant (Latin for "singing apart"), the process of two voices singing the same melody at different pitches separated by a constant interval, usually a perfect fifth or fourth. Then singers began improvising, adding melismata and other stylings. Later composers began writing parts that were not just simple transpositions of each other, and true polyphony was born. The organum as a musical genre reached its peak in the late 12th century with composers such as Perotin, and afterward was quickly superseded by the motet and the music of the troubadors. See Medieval European Music.