Louis Couperin
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.