(b Strasbourg, 21 Sept 1909; d Zürich, 27 Feb 1978). Swiss musicologist of Alsatian origin. He studied economics in Munich and Berlin – receiving the diploma in engineering in 1933. He lived in Israel from 1934 to 1952, and after working for many years as an agricultural and industrial economist he studied the harpsichord with Frank Pelleg and music theory with Paul Ben-Haim (1951–2). He completed his training with Landowska, Curt Sachs, Eduard Müller and Hindemith, under whom he received the doctorate at Zürich University in 1957 with a dissertation on the development of music theory in England. From 1956 he lived in Switzerland as an interpreter and teacher, and in 1961 he was appointed lecturer at the Zürich University musicology department. In 1970–71 he was visiting professor at the University of Iowa and in 1971–2 at Indiana University.
Jacobi’s research centred on the theory and practice of music in the 17th and 18th centuries. As well as making a complete edition of Rameau’s theoretical works, a subject to which he devoted numerous writings, he was concerned with Baroque performing practice, particularly of harpsichord music, and the continuo. Jacobi wrote extensively on Albert Schweitzer, a family friend, and edited his writings on music. In years of collecting he built up an important music library, which included original sources of music theory from the Middle Ages to the present, French Baroque harpsichord music and more than 300 Schweitzer autographs. For his work on Rameau the French government appointed him a Chevalier de l’Ordre des Arts et des Lettres in 1975.