Carl Nielsen was, according to The New Penguin Dictionary of Music, a Danish composer, reckoned his country's greatest and influencing many younger Danish composers; director of the Royal Danish Conservatory, 1930; also conductor, and formerly violinist. In 1891-2 composed his symphony no. 1, probably the first ever to begin in one key and end in another (progressive tonality) - a principle much evident in his succeeding five symphonies and other works. These include concertos for flute, for clarinet, for violin; operas "Saul and David" and "Masquerade"; chamber music (Serenata); organ work "Commotio".