Guillaume Costeley (c. 1530o1606) was a French composer and organist active at the royal court, and (importantly) in Baïf’s académie de poesie et de musique. He is credited with over 100 chansons, which range widely among the idioms current in the later sixteenth century (musique mesurée, chromatic pieces, and others, too). His Musique de Guillaume Costeley (1570) gathers together most of his secular music. The chansons published by Du Chemin reveal something of his compositional skills at the very outset of his Parisian career. Irving Godt, “Costeley, Guillaume,” New Grove 2, VI, 534-37.