thumb|Illuminated chansonnier by Heinrich Isaac, showing the beginning of his four-voice motet Palle, palle; probably written in Florence in the 1480s and copied during that period. Palle (Italian for "balls") is a reference to the coat-of arms of the Medici family, his employers at the time.|300px
Heinrich Isaac (ca. 1450 – 26 March 1517) was a Netherlandish composer of south Netherlandish origin during the Renaissance era. He wrote masses, motets, songs (in French, German and Italian), and instrumental music. A significant contemporary of Josquin des Prez, Isaac influenced the development of music in Germany. Several variants exist of his name: Ysaac, Ysaak, Henricus, Arrigo d'Ugo, and Arrigo il Tedesco among them. (Tedesco means "Flemish" or "German" in Italian.)
Early life
Little is known about Isaac's early life (or indeed what he called himself), but it is probable that he was born in the Brabant. During the late 15th century, standards of music education in the region were excellent, and he was probably educated in his homeland, although the location is not known. Sixteenth-century Swiss music theorist and writer Heinrich Glarean claimed Isaac for Germany by dubbing him "Henricus Isaac Germanus", but in his will Isaac called himself by the patronymic "Ugonis de Flandria", 'Hugo's [son] from Flanders'. A writer in the Milanese Revista critica della letteratura italiana, June 1886, speculated that this patronymic might be connected to 'Huygens' and discovered the name "Isaacke" in the town archives of Bruges.
Career
Heinrich Isaac's career spanned well over thirty years and allowed him to travel far from his homeland of Flanders into Germany, Italy, and Austria, as well as other parts of central Europe. While the absence of plentiful primary sources makes it hard for us to map out Isaac's life, piecing together the sources we do have along with the works he wrote gives us a good picture of just how popular this Franco-Flemish composer was in his time. Isaac was probably writing music by the 1470s, and the first document mentioning his name dates back to 15 September 1484, placing him in Innsbruck as a singer for Duke Sigismund of Austria, of the House of Habsburg. The following year Isaac migrated to Florence, since documents show that by July 1485 Isaac had become employed as a singer at the church Santa Maria del Fiore. By the middle of 1491, he was designated as a singer at Santissima Annunziata, a position that he held until 1493.
Several documents illustrate Isaac's long stay in Florence under the employment of Santa Maria del Fiore and Santissima Annunziata as a singer, and also suggest that he may have developed a close working-relationship with Lorenzo de' Medici. It is speculated that it was Medici who may have summoned Isaac to Florence from Innsbruck in 1484. Previously, Isaac had been identified as an organist to Lorenzo but the Isaac who served at this post is now known to have been Isaac Argyropoulos. During his presence in Florence from 1484 until the end of 1496, Isaac probably composed several masses, motets and secular songs, including missa "J'ay pris amours" and the carnival song "Hora è di Maggio". In 1487 Isaac composed the piece "A la battaglia" to commemorate the battle between Genoa and Florence for the castle Sarzanello although there is much debate over the exact date and purpose of the piece. Isaac's relationship with Lorenzo de' Medici must have been fairly close, because allegedly between 1488 and 1489 he composed the music for a play called "San Giovanni e San Paolo", written by Medici himself. Moreover, when Lorenzo died in April 1492 Isaac composed two motets in his memory. Lorenzo's son Piero inherited everything he owned, including his musical groups. In September 1492 Piero took his musical groups to Rome to perform for the coronation of Pope Alexander VI.
During his first stay in Florence Isaac also had dealings with a Florentine named Piero Bello, whose daughter Bartolomea was Isaac's wife. Although the actual date of the marriage is unknown, records imply that it may have been arranged for Isaac by Lorenzo de' Medici when he summoned Isaac from Flanders. On 15 August 1502, Isaac wrote his first will which included names of his proprietors, alluding to the fact that he was doing well to care for his wife and property should anything happen to him. He then traveled to Ferrara to the Este court where he wrote the motet "La mi la sol la sol la mi" in merely two days and competed with Josquin for employment: a famous letter from the agent of the Este family compared the two composers, saying that "[Isaac] is of a better disposition among his companions, and he will compose new works more often. It is true that Josquin composes better, but he composes when he wants to and not when one wants him to."
Between 1505 and 1512 there are records of Isaac having dealings in Augsburg, Florence and Constance (see Konstanz), the latter in which he compiled his largest set of works: Choralis Constantinus. This monumental collection of mass propers was commissioned by the Constance cathedral on 14 April 1508 and completed by Isaac and his student Ludwig Senfl by the winter of 1509. Isaac and Bartolomea were almost definitely back in Florence by this time since the completed Choralis Constantinus had to be mailed to the cathedral.
On 4 January 1512 Isaac bartered his house in Florence for a smaller one, signifying his settling down. He and his wife probably remained there except for a few short trips until his death. Isaac also made a point to revise his will on 24 November 1512 in which he requested that a mass be said every year forever at Santissima Annunziata or another church should Annunziata be unable. Bartolomea would be able to pay for these masses with provisions. On the recommendation of Pope Leo X and of his brother Giuliano de' Medici, he was given an honorary position as chief of the Chapel of Polyphonic Music at Santa Maria del Fiore on 30 May 1514, which served as a pension. Isaac also continued to receive payments from the court of Maximilian I regardless of his living in Florence. Music composed by Isaac included masses, motets, songs in French, German, and Italian, as well as instrumental music. His best known work may be the song "Innsbruck, ich muss dich lassen", of which he made at least two versions. It is possible, however, that the melody itself is not by Isaac, and only the setting is original. The same melody was later used as the theme for the Lutheran hymn "O Welt, ich muss dich lassen", which was the basis of works by Johann Sebastian Bach, including his St Matthew Passion and Johannes Brahms.
Of his settings of the ordinary of the mass, 36 survive; others are believed to have been lost. Numerous individual movements of masses survive as well. But it is composition of music for the Proper of the Mass – the portion of the liturgy which changed on different days, unlike the ordinary, which remained constant – which gave him his greatest fame. The huge cycle of motets which he wrote for the mass Proper, the Choralis Constantinus, and which he left incomplete at his death, would have supplied music for 100 separate days of the year. Another famous motet by Isaac is Optime pastor (Optime divino), written for the accession to the papacy of Medici pope Leo X. This motet compares the Pope to a shepherd capable of soothing all of his flock and binding them together.
While in the service of the Medici in Florence, Isaac wrote a lament on the death of Lorenzo de' Medici, Quis dabit capiti meo aquam (1492), which set words by Lorenzo's favorite poet, Angelo Poliziano.