WEILL, Kurt Julian (1900–1950). A German composer, active from the 1920s, and in his later years in the United States. He was a leading composer for the stage who was best known for his fruitful collaborations with Bertolt Brecht. With Brecht, he developed productions such as his best-known work The Threepenny Opera, which included the ballad "Mack the Knife". Weill held the ideal of writing music that served a socially useful purpose (Wikipedia ).