Philippe de Vitry is most famous in music history for the Ars nova notandi (1322), a treatise on music attributed to him which lent its name to the music of the entire era. While his authorship and the very existence of this treatise have recently come into question, a handful of his musical works do survive and show the innovations in musical notation, particularly mensural and rhythmic, with which he was credited within a century of their inception. Such innovations as are exemplified in his stylistically-attributed motets for the Roman de Fauvel were particularly important, and made possible the free and quite complex music of the next hundred years, culminating in the Ars subtilior. In some ways the "modern" system of rhythmic notation began with the Ars Nova, during which music might be said to have "broken free" from the older idea of the rhythmic modes, patterns which were repeated without being individually notated. The notational predecessors of modern time meters also originate in the Ars Nova.
He is reputed to have written chansons and motets, but only some of the motets have survived. Each is strikingly individual, exploiting a unique structural idea. He is also often credited with developing the concept of isorhythm (an isorhythmic line consists of repeating patterns of rhythms and pitches, but the patterns overlap rather than correspond; e.g., a line of thirty consecutive notes might contain five repetitions of a six-note melody or six repetitions of a five-note rhythm).
Five of his three-part motets have survived in the Roman de Fauvel; an additional nine can be found in the Ivrea Codex.