Heinrich Isaac (ca. 1450-1517) was a versatile and prolific Flemish composer of both secular and church music. He was one of the greatest masters of High Renaissance music.
Little is known of the early life of Heinrich Isaac. He asserted that he came from Flanders. His birth date is believed to be within a few years of the mid-15th century. He was undoubtedly trained in the Low Countries and remained there until 1484, when Lorenzo de' Medici, impressed by his reputation, invited Isaac to Florence. For 10 years he worked at the principal churches of the city as composer, singer, and choir director.
Isaac was also a composer for the Medici household and taught music to Lorenzo's children. During this decade he composed many carnival songs (now lost) to the poems of his wealthy patron. With the fall of the Medici and their expulsion from Florence (1494), Isaac lost his posts and was obliged to seek employment with the Hapsburgs at Vienna and Innsbruck. He did, however, maintain a house in Florence until his death, partly because he loved the city and partly in deference to his Florentine wife.
In 1496 Emperor Maximilian of Austria appointed Isaac imperial court composer at Vienna, a title he retained for the rest of his life. His church music for the German liturgy as well as his German songs all probably date from this time. As court composer he was required only to furnish the court and chapel with musical compositions; continuous attendance on the monarch was not required, so the composer lived far from Vienna for many years. Maximilian also seems not to have objected to Isaac's composing for other rulers or civic authorities while on the imperial payroll. Isaac received payments from the Elector of Saxony (1497-1500) and wrote music for the Duke of Ferrara (1503-1505). A commission from the German city of Constance in 1508 produced a monumental series of polyphonic Mass Propers (Introits, Alleluias, Sequences, Communions) for feast days celebrated in the city. These pieces, together with other Mass Propers by Isaac, were published posthumously in three volumes as the Choralis Constantinus (1550-1555).
In 1512 the Medici returned to Florence, and a year later Giovanni de' Medici, Isaac's former student, ascended the papal throne as Leo X. Isaac thereupon requested papal assistance for reinstatement to his former positions at Florence. When these negotiations were successfully completed in 1514, Isaac journeyed north for release from further obligations to his imperial master. With characteristic magnanimity Emperor Maximilian permitted the composer to return to Florence without loss of salary and, in effect, gave him a pension to enjoy his last days in Italy. Several months after drawing up his final (third) last will and testament, Isaac died in Florence on March 26, 1517.
Isaac's music owes much to the Netherlandish style he learned in his homeland. Among his more conservative traits is a persistent allegiance to the traditional cantus firmus. He wrote fewer pieces without a borrowed tune than many contemporaries who were then moving more toward free composition. Among the progressive features of his style is his use of imitation and melodic and rhythmic equality of voice parts. Intricate canons and notational artifices are occasionally found in the Masses, but they almost always serve a musical purpose. Similarly, Isaac's melodic lines may sometimes look intricate and fussy, but they never sound so to the exclusion of their musical interest. That he was a great melodist is shown by his song Innsbruck ich muss dich lassen, a tune destined to have a strong influence on the later German song.
Unlike some of his contemporaries, Isaac was equally adept at writing religious and secular music: German, French, and Italian songs; instrumental pieces; Masses for four to six voices and Propers for the entire church year; separate Credos; and motets. He had the rare ability to assimilate different national styles and yet preserve his own idiom.
Isaac's music is discussed in Gustave Reese, Music in the Renaissance (1954; rev. ed. 1959), and J. A. Westrup and others, eds., The New Oxford History of Music, vol. 3 (1960). For a summary of music in the Renaissance see Paul Henry Lang, Music in Western Civilization (1941).