Guillaume Dufay (ca. 1400–1474) is regarded as the foremost French composer of the early fifteenth century. He was a widely traveled
and educated cleric, having first studied and worked in Italy, then later in what is now Switzerland and France. It was common practice to
set the Ordinarium Missa in polyphony, which was sung by a specially trained choir, while the Proprium Missa was sung by the Schola Cantorum
in plainsong. The plainsong was sometimes sung in parts, the result of the impossibility of mixed voices to sing in unison, so the singing was
done in octaves or occasionally other intervals. Solos were sung by trained choristers in pairs, trios, or quartets. The structure of the mass
also permitted optional incremental music in the form or tropes or motets, which served to prevent silence when actions extended beyond the
duration of the existing music, often heightening the theme of the service and providing points of beauty.