the composer arnold schoenberg (1874–1951) wrote pieces which were atonal (meaning that they did not sound as if they were in any clear musical key). later, schoenberg invented a new system for writing music called twelve-tone system. music written with the twelve-tone system sounds strange to some, but is mathematical in nature, often making sense only after careful study. pure twelve-tone music was popular among academics in the fifties and sixties, but some composers such as benjamin britten use it today, when it is necessary to get a certain feel.