The king helped him to procure a canonry in Reims, which was confirmed in 1335; Machaut settled there circa 1340, although he continued in royal service until the king's death (1346).

He then served various members of the French high nobiIity, including John, Duke of Berry, his later years being dedicated to the manuscript compilation of his works.

With his prolific output of motets and songs, Machaut was the single most important figure of the French Ars Nova. He followed and developed the guidelines of Philippe de Vitry's treatise Ars nova and, in particular, observed Vitry's unprecedented advocation of duple time in many of his works, even in his setting of the Ordinary of the Mass.

Only in some of his lais and virelais and the Hoquetus David did he consistently adhere to 13th-century rhythmic patterns and genres. His own rhythmic style is novel in its use of variety and motivic interest, particularly through syncopation, and in his development of isorhythmic techniques (which he often extended to all voices): all but three of his 23 motets, and four of the movements of the Messe de Nostre Dame, are isorhythmic.

The mass is one of the earliest polyphonic settings of the Mass Ordinary; the four isorhythmic movements are based on Gregorian tenors, while the Gloria and Credo are freely constructed.

In secular music, Machaut set a wide range of poetic forms, all of which are illustrated in his long narrative poem, the Remede de Fortune (probably an early work). While the relationship between text and music is most closely observed in the monophonic lais and virelais, a highly flexible approach is adopted in the three-voice motets so that the subtle treatment of the text avoids the symmetricality of complete isorhythm.

His inventive approach to isorhythm resulted in freely-constructed introductions to five of his Latin motets. More progressive features of Machaut's style - an increased awareness of tonality, the use of unifying rhythmic motifs - are found in his polyphonic settings of rondeaux and ballades, while melodic considerations are to the fore in his virelais.

Typical of Machaut's compositional flair and imagination is the rondeau Ma fin est mon commencement in which the text provides the key to an ingenious canon.