What is triplum?

A triplum is a term used in medieval Music Theory to describe a specific type of polyphonic composition that consists of three simultaneous melodies, typically with a prominent cantus firmus (a fixed melody). The most common form of triplum can be found in the context of the Notre Dame school of polyphony, where it often involves intricate rhythmic and melodic interplay among the three voices. This style contributed significantly to the development of early Western music, particularly in the transition from monophonic to polyphonic textures.