Johann Ernst III (22 June 1664 in Weimar – 10 May 1707 in Weimar), was a duke of Saxe-Weimar.
Johann Sebastian Bach and Weimar
In the first half of 1703, Johann Sebastian Bach served as a court musician at Weimar. He was still in his teens and developing a reputation as an organist. Little is known of his precise role (he may have been taken on as a violinist rather than a keyboardist), but as a mere musician, he most likely was considered a servant. He left to take up a position as organist of a church at Arnstadt.
Bach returned to Weimar in 1708, after Johann Ernst's death, as court organist. Bach worked with one of Johann Ernst's sons, also called Johann Ernst, who had a keen interest in music. The prince's interest in collecting music was sufficiently well known that in 1713, when one of Bach's pupils, P. D. Kräuter, was requesting leave of absence to study in Weimar, he mentioned the French and Italian music that the prince was expected to introduce there.
The prince also composed, and Bach wrote the Organ Concerto No.1 in G Major, BWV 592, and Concerto for Organ solo in C major, BWV 595, after a theme by the prince.