In the context of Medieval music, what is a clausula?

In the context of Medieval music, a clausula refers specifically to a form of early polyphonic music, particularly associated with the development of organum. During the Medieval period, composers began to explore the concept of adding a second voice to chant melodies, which led to the creation of polyphony. The clausula typically involves the addition of a contrasting melodic line over a pre-existing chant, allowing for greater harmonic complexity and texture.

This form showcased early attempts at polyphony, where voices moved independently while still being rooted in liturgical chant. Composers would create clausulae that were often interchangeable within the context of a larger chant, demonstrating both innovation and adherence to traditional forms of music. This practice was crucial in the evolution of Western music, paving the way for more intricate polyphonic structures in later musical styles.