Jacobus of Liège (EN)

Jacobus of Liège, Jacques de Liège, Jacobus Leodiensis, Jacobus de Oudenaerde, Jacobus de Montibus, Magister Jacobus de Ispania. One of the most prominent music theorists of the first half of the 14th century, author of the monumental work Speculum musicae in seven books, dated to the third decade of the 14th century. Speculum musicae is preserved in three 15th-century manuscripts of Italian provenance, but only one (Paris, Bibliothèque Nationale, Lat. 7207) contains the entire work. The second treatise in this codex is Musica speculativa by Johannes de Muris, and despite fundamental differences between the views expressed in the two treatises, he was long credited with the authorship of Speculum musicae. The name “Jacobus”, given in the form of an acrostic composed of the first letters of the opening chapters of the successive books of the work, was indicated by the author himself.

The biography of the author of Speculum musicae remains almost completely unknown, apart from the details he himself revealed. He studied in Paris. He read the treatises of Johannes de Muris and Philippe de Vitry, whom he may have known personally. Liège was considered his place of origin based on the characteristics of the musical works he quoted. However, the approximate dates of his life and place of birth and death (*ca. 1260 Liège, †after 1330 Liège) are not documented. He was identified successively with a canon in Liège and a professor at the University of Paris in 1313 named Jacobus de Oudenaerde, and with a theorist named Jacobus de Montibus (the city of Mons in present-day Belgium), quoted in one of the treatises handed down in the Berkeley manuscript (Jean Gray Hargrove Music Library, ref. no. 744 olim Phillipps 4450, dated Paris 1375). However, “Magister Jacobus de Ispania” appears as the author of a musical treatise mentioned and described in an inventory from 1457 kept in the Archivio Capitolare in Vicenza. According to the description contained therein, this treatise consisted of seven books, the first letters of which formed the name “Jacobus,” indicating that it was a treatise by Jacobus. The question of the identity of the author of Speculum musicae has not yet been resolved.

Speculum musicae constitutes a work unique in its scope, an exhaustive and creative synthesis of the achievements of Latin music theory, from Boethius and the ancient theory transmitted by him through to the achievements of the ars nova. Book I of Speculum is devoted to methodological issues (the definition of music, the place of music in the system of sciences, the classification of music) and the theory of sound and number. Book II addresses the problem of consonance and examines, from this perspective, intervals ranging from the unison, through those resulting from the division of the whole tone, to compound intervals extending to the double octave with major sixth, which constitute the framework of the ‘model’ musical scale G Graecum – ee duplicatum. Jacobus made a thorough comparison of the Pythagorean system with the hexachordal system. Book III discusses primarily the issue of proportion. Book IV presents a very detailed classification of intervals within an ambitus exceeding three octaves; here Jacobus provided a definition of cadence understood as “a certain order and natural tendency of a less perfect consonance toward a more perfect one.” Book V is devoted to the problems of monochord division, while Book VI deals with the issue of musica plana. The last book, in which Jacobus presented his views on musica mensurabilis, includes, among other things, a polemic with the concepts of Johannes de Muris and Philippe de Vitry, and in the final chapters – a criticism of the innovations introduced during the ars nova period and a defense of the values represented by ars antiqua.

The authorship of three other treatises – Tractatus de consonantiis musicalibus, Tractatus de intonatione tonorum, and Compendium de musica – is uncertain.

Literature: R. Hirschfeld Johann de Muris. Seine Werke und seine Bedeutung als Verfechter des Classischen in der Tonkunst. Eine Studie, Leipzig 1884; W. Grossmann Die einleitenden Kapitel des Speculum Musicae von Johannes de Muris. Ein Beitrag zu Musikanschauung des Mittelalters, Leipzig 1924 (includes Speculum musicae, Book 1, chapters 1–19); H. Besseler Studien zur Musik des Mittelalters, part 1: Neue Quellen des 14. und beginnenden 15. Jahrhunderts, “Archiv für Musikwissenschaft” VII, 1925; G. Pietzsch Die Klassifikation der Musik von Boetius bis Ugolino von Orvieto, Halle 1929; J. Smits van Waesberghe Muziekgeschiedenis der Middeleewen, 2 vols., Tilburg 1936–46; J. Smits van Waesberghe Some Music Treatises and their Interrelation – a School of Liège (c. 1050–1200), “Musica Disciplina” III, 1949; S. Clercx-Lejeune Jacques d’Audenaerde ou Jacques de Liège, “Revue Belge de Musicologie” VII, 1953; R. Bragard Le Speculum musicae du compilateur Jocgues de Liège, “Musica Disciplina” VII, VIII, 1953, 1954; F. Smith Jacques de Liège, an Anti-Modernist?,  “Revue belge de Musicologie / Belgisch Tijdschrift voor Muziekwetenschap” 17, 1/4, 1963; J. Ballke Untersuchungen zum sechsten Buch des Speculum musicae des Jacobus von Lüttich unter besonderer Berücksichtigung der Tetrachord- und Moduslehre, Frankfurt 1982; O. Ellsworth The Berkeley Manuscript, Lincoln, Nebraska 1984; K. Slocum Speculum musicae: Jacques de Liège and the Art of Musical Number, in: Medieval Numerology, ed. R.L. Surles,  New Jork 1993; K. Desmond New Light on Jacobus, Author of Speculum musicae, “Plainsong and Medieval Music” 9/1, 2000; M. Bent Jacobus de Ispania? – Ein Zwischenbericht, in: Nationes, Gentes und die Musik im Mittelalter, ed. F. Hentschel, M. Winkelmüller, Berlin 2014; M. Bent Magister Jacobus de Ispania, Author of the Speculum Musicae, Ashgate 2015; R.C. Wegman Jacobus de Ispania and Liège, “Journal of the Alamire Foundation” 8/2, 2016, R.C. Wegman Jacobus de Ispania, The Mirror of Music, Book Seventh, Lamotte 2017; K. Desmond Music and the moderni, 1300–1350. The ars nova in Theory and Practice, Cambridge 2018; A. Zayaruznaya Old, New, and Newer Still in Book 7 of the Speculum musicae, “Journal of the American Musicological Society” 73/1, 2020; E. Witkowska-Zaremba Johannes de Muris’s Musica Speculativa cited by Jacobus de Ispania, “Plainsong and Medieval Music” 31/1, 2022.