The main genre of Costeley's music was the chanson. He was probably the first composer, however, to employ the use of the term "air" to his chansons. The term applied to musical themes repeated and only slightly varied from stanza to stanza of various poems set to music, but, the rhythms were consistent throughout. Costeley was familair with and may have had a mutual influence with respect to such musicians as Arcadelt, Sandrin, Ronsard, Belleau, Baif and Maillard. He was in service to the Italian court and hence, the Queen Mother Catherine de'Medici. Costeley attempted a variety of nuances within the content of his compositions. These adaptations included microtones, multiple accidentals, vertical harmonies as opposed to counter points, and augmented and diminished intervals. Keyboard music was Costeley's forte but little if any French keyboard music from this time period remains; accordingly, his only extant piece holds a place of privilege. ~ Keith Johnson, All Music Guide