MÜLLER, mụ'lẽr. A family of celebrated quartet players. They were the sons as well as pupils of the principal musician to the Duke of Brunswick, and were all of them born in the city of Brunswick. Carl Friedrich (1797-1873) was first violin in the quartet and was also concertmaster to the Duke. Theodor Heinrich (1799-1855) was the viola player. August Theodor (1802-75) played the cello, and Franz Ferdinand Georg (1808-55) was the second violin. They were especially educated by their father for quartet work, and were conceded to have reduced the art of string quartet playing to a degree of perfection previously unknown. They were ambitious for greater fame than could be obtained within their own limited environment, and were particularly handicapped by the Duke of Brunswick, in whose employ they were, who had formulated the order that none of his musicians should participate in any musical performance outside that connected with his own corps. In 1830 they resigned their employment, and made their first appearance in Hamburg, where they met with such success that they were invited to Berlin, in which city they were received with great enthusiasm. An extended tour throughout Germany followed, and in 1837 they performed in Paris. Other successful tours made them known throughout the world. They confined their programmes almost entirely to the works of Haydn, Mozart, and Beethoven, and were also a very important influence in raising and establishing a higher standard of musical appreciation.