1. Ars Nova was a style of music that developed in 14th century France and Italy, outlined by theorist Philippe de Vitry in his treatise of the same name. 2. De Vitry introduced innovations like motets with 3 voices, hocket technique, and imperfect consonances that had to resolve. Mensural notation also became more complex during this time period. 3. Guillaume de Machaut was a renowned 14th century poet and composer who further developed Ars Nova styles and techniques in genres like motets, masses, and chansons.