d’Alembert, Jean-le-Rond, French philosopher and encyclopedist; b. Paris, Nov. 16, 1717; d. there, Oct. 29, 1783. He was the illegitimate child of one Mme. de Tencin and an artillery officer named Destouches; his mother abandoned him on the steps of the church of St. Jean-le-Rond, which name was subsequently attached to him. Later his father acknowledged him and enabled him to study. He was sent to the Mazarin Coll., and progressed rapidly in mathematics. He also was interested in theoretical musical subjects and published several treatises on acoustics and on the theory of music: Recherches sur la courbe, que forme une corde tendue mise en vibration (1749), Recherches sur les vibrations des cordes sonores and Recherches sur la vitesse du son (both in Opuscules mathématiques, Paris, 1761–80), Reflexions sur la musique en général et sur la musique française en particulier (1754), and Reflexions sur la théorie de la musique (1777). His best- known work on music was Éléments de musique, théorique et pratique, suivant les principes de M. Rameau (1752), which went into 6 eds. He contributed several articles on music to the famous Encyclopédie, which he ed. with Diderot.
J. Bertrand, d’A. (Paris, 1889).
—Nicolas Slonimsky/Laura Kuhn/Dennis McIntire