Edwardian musical comedy held the London stage (together with foreign operetta imports) until World War I and was then supplanted by increasingly popular American musical theatre and comedies by Noel Coward, Ivor Novello and their contemporaries. The motion picture mounted a challenge to the stage. At first, films were silent and presented only a limited challenge to theatre. But by the end of the 1920s, films like The Jazz Singer could be presented with synchronized sound, and critics wondered if the cinema would replace live theatre altogether. Some dramatists wrote for the new medium, but playwriting continued.