听力原文： Accustomed though we are to speaking of the films made before 1927 as 'silent', the film has never been, in the full sense of the word, silent. From the very beginning, music was regarded as an indispensable accompaniment when the Lumiere films were shown at the first public film exhibition in the United States in February 1896, they were accompanied by piano improvisations on popular tunes. At first, the music played bore no special relationship to the films an accompaniment of any kind was sufficient. Within a very short time, however, the incongruity of playing lively music to a solemn film became apparent, and film pianists began to take some care in matching their pieces to the mood of the film. As movie theaters grew in number and importance, a violinist, and perhaps a cellist, would be added to the pianist in certain cases, and in the larger movie theaters small orchestras were formed. For a number of years the selection of music for each film program rested entirely in the hands of the conductor or leader of the orchestra, and very often the principal qualification for holding such a position was not skill or taste so much as the ownership of a large personal library of musical pieces. Since the conductor seldom saw the films until the night before they were to be shown, the musical arrangement was normally improvised in the greatest hurry. To help meet this difficulty, film distributing companies started the practice of publishing suggestions for musical accompaniments. In 1909, for example, the Edison Company began issuing with their films such indications of mood as 'pleasant', 'sad', 'lively'. The suggestions became more explicit, and so emerged the musical cue sheet containing indications of mood, the titles of suitable pieces of music, and precise directions to show where one piece led into the next. Certain films had music especially composed for them. The most famous of these early special scores was that composed and arranged for D. W Griffith's film Birth of a Nation, which was released in 1915. When were the Lumiere films shown at the first public film exhibition in America?