Questions: The Messe de Nostre Dame, the first complete polyphonic setting of the Ordinary of the Mass, was written by which composer?

The answer is Guillaume de Machaut.

Pérotin was a composer associated with the Notre Dame school of polyphony in the late 12th and early 13th centuries. He is known for his contributions to the development of early polyphonic music, but he did not compose the Messe de Nostre Dame.

Hildegard of Bingen was a German abbess, writer, composer, and philosopher of the 12th century. She is known for her monophonic compositions and liturgical songs, but she did not write the Messe de Nostre Dame.

Guillaume de Machaut was a French composer and poet of the 14th century. He is credited with composing the Messe de Nostre Dame, which is the first complete polyphonic setting of the Ordinary of the Mass by a single composer.

Léonin was another composer associated with the Notre Dame school of polyphony, active in the late 12th century. Like Pérotin, he contributed to the development of early polyphonic music but did not compose the Messe de Nostre Dame.