Composer. One of the most gifted of high Renaissance-era musicians, regarded by his contemporaries as second only to Josquin Des Prez. Known facts of Isaac's early life are scant. He claimed he was born in Flanders but the earliest records (1484) show him traveling to Florence to begin his lifelong association with the Medici family. Until 1493 he was organist and singer at the Florence Cathedral and he may have been tutor to Lorenzo the Magnificent's children. In 1497 Isaac was given the non-exclusive post of court composer to Hapsburg Emperor Maximilian I, with duties that took him to Vienna, Innsbruck, Konstanz, and other Germanic centers, though he continued to maintain a residence in Florence. He retired there on a Medici pension in 1514. In his will Isaac left provisions for his burial in the 13th Century Church of Maria di Servi, which was then being rebuilt as the Church of SS. Annunziata; the tomb was lost in subsequent construction. Isaac was perhaps the most versatile and cosmopolitan composer of his time. Equally adept in sacred and secular music, he wrote to order and fitted his style to the requirements of a commission without sacrificing his strongly personal voice. Outstanding among his works is the "Choralis Constantinus" (3 volumes, published in 1555), a monumental cycle of 99 Mass Proper settings for the liturgical year. He also produced some 36 Masses and 80 songs; the most famous of the latter are "Ne piu bella di queste" (a hymn to his beloved Florence) and "Innsbruck, ich muss dich lassen", later adapted by J.S. Bach and Brahms. Although he spent most of his career in Italy, Isaac had his broadest influence in Germany, where his music helped popularize the polyphony of the Franco-Flemish school. It also had a profound influence on an important 20th Century composer, serialist Anton Webern.