Johannes de Grocheio (or Grocheo) (Ecclesiastical Latin: [jɔˈan.nɛs dɛ ɡrɔˈkɛj.jɔ]; c. 1255 – c. 1320) was a Parisian musical theorist of the early 14th century. His French name was Jean de Grouchy, but he is best known by his Latinized name. He was the author of the treatise Ars musicae ("The Art of Music") (c. 1300), which describes the functions of sacred and secular music in and around Paris during his lifetime. Biography Johannes de Grocheio, originally named Jean de Grouchy, likely grew up in a wealthy family that controlled a fiefdom in Normandy. Grocheio studied music and philosophy in Paris, but there is no evidence that he received a degree. Despite the lack of such evidence, he is credited as magister (master) and regens Parisius (resident teacher in Paris in the Darmstadt manuscript, although the latter title was added to the manuscript after it was copied. Grocheio may also have taught at the Basilica of St. Denis based on the plainsong he describes in the section on church music (musica ecclesiastica) in the Ars musicae. Not much else is known about Grocheio's life because any biographical information comes from the Ars musicae as well as scholarly research and speculation. Ars musicae Topics discussed in treatise Grocheio wrote about several principles of music in thirteenth-century Paris that he had observed. Grocheio's divides music into three categories: musica vulgaris ("music of the people"), musica mensurabilis ("measured music"), and musica ecclesiastica ("church music"). He also discusses music theory and compositional techniques such as mensural notation and musica ficta. Grocheio takes a scholastic takes approach in his treatise, rejecting Boethius' threefold division of music into musica mundana (music of the spheres) musica humana (music of the human body), and musica instrumentalis (vocal or instrumental music). Instead, he uses a technique of classification similar to Aristotle by taking a taxonomical approach used in several of Aristotle's works. Grocheio also consults and criticizes the works of many other music theorists, mathematicians, and philosophers such as Plato, Pythagoras, Johannes de Garlandia, Franco of Cologne, Nicomachus, and several others. Musica vulgaris Grocheio considers most of the music that the laypeople enjoy to be musica vulgaris. He describes this music as being able to ease the fears and sufferings of the people. Grocheio consulted a monk named Clement at the Abbey of Lessay as his source for musica vulgaris. Grocheio further specifies that there are two kinds of