In the period between the two world wars, Paul Hindemith was oneof the leading composers in Germany and an articulatespokesman for the values of discipline, technique, and communication in music. He began his career as a violinist at the conservatory in Frankfurt in 1908; by 1915 he was the leader of the Frankfurt Opera Orchestra. Following military service, he returned to the Frankfurt Opera, but was now playing the viola, the instrument on which he would later develop a reputation as a major virtuoso. He began to attract notice as a composer in 1922, leading to an appointment at the Hochschule für Musik in Berlin in 1927. Some of his lurid one-act operas and naive political statements brought him into conflict with the Nazi regime in Germany. As a result, the work generally considered to mark the establishment of his mature style, the opera Mathis der Maler, met with a government boycott in 1934. The issue became a cause célèbre, marked by a public letter from the conductor Wilhelm Furtwängler in defense of Hindemith and responding to public condemnation from Chancellor Adolf Hitler and his minister for cultural affairs, Joseph Goebbels. Hindemith emigrated to Switzerland in 1938, later moving to the United States where, with his lively intellect and fresh ideas, he exerted considerable influence as professor of music at Yale University from 1940 to 1953. Following his return to Germany, he became increasingly involved in conducting, particularly concerts of his own works.