ISAAK, HEINRICH

International polyphonic composer, b. Brabant, North Flanders c. 1450; d. Florence, Italy, 1517. Isaak is generally recognized to be of Netherlandish origin, although earlier biographers held him to be German or even Bohemian. His lineage is attested by the typically Flemish style of his sacred music, but even more irrefutably by his self-designation as filius Ugonis de Flandria in his will. Nothing is known of his early years; he first emerged in 1484 as a guest at the Innsbruck court, possibly while en route to Florence for service at the court of Lorenzo de' Medici ("the Magnificent"). His departure

from Flanders at about this time was perhaps occasioned by the dispersion of the Burgundian musical establishment, following the death of Mary of Burgundy in 1482. Since Archduke Maximilian (later Holy Roman Emperor) resided in Flanders for some 12 years after his marriage to Mary of Burgundy in 1477, he undoubtedly knew Isaak's talents; this accounts for Isaak's quick employment by the emperor in 1494, while encamped before Pisa, after the death of Lorenzo. Isaak remained nominally in the emperor's service until his death, although he was apparently permitted to spend long periods away from court. New evidence from Italian documents would indicate that he spent most of his time after 1508 in Italy (see D'Accone in bibliography).

Isaak was a skilled and versatile composer, equally at home with sacred and secular music. Undoubtedly his magnum opus was the unfinished Choralis Constantinus, which was planned to furnish polyphonic settings of certain items of the Proper of the Mass for the entire liturgical year. These were designed for alternatim performance, since only alternate lines or verses were composed. The MS was completed and prepared for publication (3 v. Nürnberg 1550–55) by his greatest student, Ludwig senfl, who did not see his task fulfilled, since he died in 1543. An important feature of the Choralis Constantinus is the polyphonic setting of 47 sequences, which makes this the most comprehensive single source for the early 16th-century sequence-motet.

Bibliography: Works. Choralis Constantinus, Book I, ed. e. bezecny and w. rabl (Denkmäler der Tonkunst in Österreich 10; Graz 1959), Book II, ed. a. von webern (ibid., 32; 1959), Book III, ed. l. e. cuyler (Ann Arbor 1950); Weltliche Werke, ed. j. wolf (Denkmäler der Tonkunst in Österreich 28; Graz 1959); Five Polyphonic Masses, ed. l. e. cuyler (Ann Arbor 1956). Literature. p. blaschke, "H. Isaak's Choralis Constantinus, " Kirchenmusikalisches Jahrbuch, 26 (1931) 32–50. l. e. cuyler, "The Sequences of Isaac's Choralis Constantinus, " Journal of the American Musicological Society 3 (1950) 3–16. f. a. d'accone, "H. Isaac in Florence: New and Unpublished Documents," Musical Quarterly 49 (1963) 464–483. g. reese, Music in the Renaissance (rev. ed. New York 1959). e. c. kempson, The Motets of Henricus Isaac (c. 1450–1517), Transmission, Structure and Function (Ph.D. diss. King's College, University of London 1998). e. lerner, "Choralis Constantinus van Heinrich Isaac," Musica Antiqua 14 (1997) 117–125. j. a. owens, "An Isaac Autograph," in Music in the German Renaissance: Sources, Styles, and Contexts, ed. j. kmetz (Cambridge, Eng. 1994) 27–53. d. m. randel, ed., The Harvard Biographical Dictionary of Music (Cambridge, Mass. 1996) 407–408. n. slonimsky, ed., Baker's Biographical Dictionary of Musicians (8th ed. New York 1992) 828. m. staehelin, "Heinrich Isaac," in The New Grove Dictionary of Music and Musicians, ed. s. sadie, v. 9 (New York 1980) 329–337.

[l. e. cuyler]