Leoninus and Perotinus dominated the twelfth-century musical world. Both were reputedly based at Notre Dame in Paris, and Leoninus was responsible for the Magnus liber organi, the 'Big Book of organum' (an organum being a polyphonic setting of plainchant), which is widely regarded as the single greatest acievement in the development of early polyphony.

• B0042ZUNJC
• Perotin
• Leonin, Perotin: Sacred Music from Notre-Dame Cathedral
• Sacred & Secular Music
• B00006L3IE