ISAAC, HEINRICH (born c. 145o), Belgian composer. The exact date and place of his birth are unknown but Cambrai has been assigned as his place of origin by some writers. About he appears to have gone to Florence and for many years he was organist at the Medici chapel. After Lorenzo di Medici's death he found his way to Vienna and obtained an appointment as composer at Maximilian's court at Innsbruck. In 1515 he re turned to Florence with a yearly pension of 15o florins. Few biographical facts have been established with certainty but the allusions found here and there in contemporary and later writ ings show him to have been recognized as one of the great musicians of his time. Until recently he was included in the group of German composers—Finck, Stolzer, Agricola and others —among whom he was the outstanding figure. The Italians called him "Arrhigo Tedesco," and his fame as a writer of Ger man songs in the latter part of his life was an added reason for assuming him to be a German ; but there seems now no doubt that he came from the Netherlands. His church music, of which much has been preserved, is masterly in form and shows great skill and ingenuity in the leading of the parts. But side by side with monumental masses he wrote, while in Florence, light secular compositions of a kind suited to the atmosphere of the Medici court.' He also helped Lorenzo with his canti carnascial
eschi for May Day celebrations. Later, at Innsbruck, he wrote the very simple and beautiful German songs on which his fame rests. Many of his melodies, some of them no doubt traditional, were treasured among the people and revived again and again to suit new words. Thus, Innsbruck ich muss dich lassen, written it is said to words by the emperor Maximilian, served for the hymn 0 Welt, ich muss dick lassen, for Paul Fleming's In alien meinen Taten, and for two chorales in Bach's Matthew Passion (Nos. 16, 44).
Of Isaac's ten published masses, five are included in Misse Heinrici Izac (Petrucci 1906) ; two in the Wittenberg edition (1541) ; Carminum and Une musque de Biscay; one in the Liber quindecim missarum (Nuremberg 1539), the famous 0 praeclara, written on one four-note subject throughout; and two in Ott's collection: Missae r3 vocum (Nuremberg 1539). There are also thirteen ms. masses preserved in the libraries in Vienna, Munich and Brussels. Motets and Psalms are con tained in upwards of forty collections published up to 5564. (See Eit ner: Bibl. der Musiksammelwerke, Berlin 1877.)