Guillaume de Machaut, sometimes spelled Machault, (c. 1300 April 1377), was an important Medieval French poet and composer. He is one of the earliest composers for whom significant biographical information is available.
Guillaume de Machaut was "the last great poet who was also a composer,". Well into the 15th century, Machaut's poetry was greatly admired and imitated by other poets including the likes of Geoffrey Chaucer.
Machaut was and is the most celebrated composer of the 14th century. He composed in a wide range of styles and forms and his output was enormous. He was also the most famous and historically significant representative of the musical movement known as the ars nova.
Machaut was especially influential in the development of the motet and the secular song (particularly the lai, and the formes fixes: rondeau, virelai and ballade). Machaut wrote the Messe de Nostre Dame, the earliest known complete setting of the Ordinary of the Mass attributable to a single composer, and influenced composers for centuries to come.
Here's the "Ensemble Organum" version of the Gloria from that page:
Interesting to read the comments on that page; apparently each recording of this mass - and most likely other music from that time and earlier - is an approximation/estimate/guess about how it originally was sung and sounded. This version seems very "Moorish" (perhaps ?), as one commenter noticed.
Here's a different version of the Machaut Messe de Nostre Dame, from "Ensemble Giles Binchois". It begins, "Gaudeamus," so I think this version must include the chant propers; Gaudeamus is the Introit for All Saints' Day - but also, I'm reading, historically for The Feast of the Assumption, which makes more sense in this circumstance, since it's the "Messe de Nostre Dame," after all. [EDIT: A commenter, Ben, helpfully notes that:
The Ensemble Giles Binchois is indeed singing Mass of the Assumption. The introit text varies according to the feast on which it is used - this version bids us rejoice 'sub honore Mariae Virginis, de cujus Assumptione gaudent angeli'.]
Thank you very much, Ben! I'll still need to look more at that and see what I find - would like to know more about "Gaudemus" and its use - but meantime, here's the piece:
Here's the Kyrie from the Ensemble Binchois:
And here's the Binchois Gloria:
Here's the Sanctus:
Here's the Agnus Dei:
There seem to be 14 videos in all of the latter version, all available if you click over there. Dominique Vellard is the guy with the curly hair; I've come across him before.
This is really beautiful music, isn't it?