Guillaume-Gabriel Nivers (c. 1632, Paris – 13 November 1714) was a French organist, composer and theorist. His first livre d'orgue is the earliest surviving published collection with traditional French organ school forms (a collection by Louis Couperin that is in manuscript does not seem to have been published. See Guy Oldham, "Louis Couperin: A New Source of French Keyboard Music of the Mid-17th Century", Recherches sur la musique française classique, Vol. I (1960), pp. 51–59). Nivers's other music is less known; however, his treatises on Gregorian chant and basso continuo are still considered important sources on 17th century liturgical music and performance practice. Life Nivers was born into a prosperous Parisian family: his father was a fermier générale (tax collector) for the bishop. Nothing is known of his early years or his musical training except that he may have received a degree from the University of Paris. In the early 1650s Nivers became organist of Saint-Sulpice, a post he would retain until 1702. In 1668 the composer married; he had one son. Nivers's subsequent career was quite illustrious. On 19 June 1678 he was chosen as one of the four organists of the Chapelle Royale—an ensemble of musicians who performed sacred music for the king. The other three organists were Nicolas Lebègue, Jacques Thomelin and Jean-Baptiste Buterne. Nivers only resigned late in life, in 1708, and was succeeded by Louis Marchand. This prestigious post was followed by another in 1681, when the composer succeeded Henri Dumont as master of music to the queen. Finally, in 1686 Nivers was in charge of the music at the Maison Royale de Saint-Louis in Saint-Cyr-l'École—a convent school for young ladies who were poor but of noble birth. Nivers apparently had difficulties with the founder of the school, Madame de Maintenon, but retained the post until his death. His colleagues at St Cyr were Jean-Baptiste Moreau, who worked there since the school's inception, and possibly Louis-Nicolas Clérambault, who may have helped Nivers from about 1710 until the latter's death in 1714. Clérambault succeeded Nivers both at St Sulpice and St Cyr. During his lifetime, Nivers was highly regarded not only as organist and composer but also as a music theorist. His treatise on composition (Traité de la composition de musique, 1667) was well known outside France and endured into the 18th century. His work in the field of Gregorian chant resulted in influential editions of