In the Middle Ages, polyphonic music was documented by an English student known as Anonymous IV, who was probably active at Notre Dame Cathedral in Paris in the 1270s or 1280s. His writings, preserved in two partial copies from Bury St Edmunds, provide valuable insights into the Notre Dame school of polyphony and name two important composers: Leoninus and Perotinus.
Leoninus, who apparently also wrote erotic poetry, created the 'Magnus liber organi'—a work considered a landmark achievement in the development of early polyphony. The monk from Bury St Edmunds describes Leoninus as a master of organum, while Perotinus excelled in discantus. Although both composers had probably died fifty years earlier, they were still considered famous and part of a vibrant tradition during Anonymous IV's lifetime.
The musical compositions of this period were characterized by complex structures, in which monophonic singing was interwoven with multifaceted polyphonic elements. Perotinus' four-part organa, such as 'Viderunt' and 'Sederunt,' are particularly highlighted by Anonymous IV. His treatise also describes various compositional genres, rhythmic modes, and rules for notation and the use of consonance and dissonance.
The production of polyphonic manuscripts in Paris followed standardized procedures. Several scribes could work on different volumes simultaneously, their approaches to the repertoire varying—from comprehensive collections to selective compilations with different decorative standards, depending on the commission and budget.
These early musical works represent a significant cultural heritage and offer insights into the development of Western music during a crucial period in its history.