Passage 4 　　Material culture refers to the touchable, material" things"--physical objects that can be seen, held,felt, used--that a culture produces. Examining a nation’s material culture can tell us about the group’s history and way of life. Similarly, research into the material culture of music can help us understand the music culture. The most vivid way, of course, is musical instruments. We cannot hear for ourselves the actual sound of any musical performance before the 1870s when the phonograph was invented, so we rely on instruments for important information about music culture, their remote past and their development. 　　Here we have two kinds of evidence: instruments well preserved and pictures of instruments in art. 　　Through the study of instruments, as well as preserved paintings, written documents, and so on, we can explore the movement of music from the Near East to China over a thousand years ago, or we can outline the spread of the influence of the eastern countries to Europe that results in the development of most of the instruments on the symphony orchestra. 　　Sheet music or printed music, too is material culture. Printed versions limit variety because they tend to standardize any song, yet folk music stimulates people to create new and different songs. Besides,the ability to read music notation (乐谱) has a far-reaching effect on musicians and, when it becomes widespread, on the music culture as a whole. 　　One more important part of music’s material culture is the influence of the electronic media-radio,record player, tape recorder, television, and video cassette, with the future promising talking and singing computers and other developments. This is all part of the" information revolution," a twentieth century phenomenon as important as the industrial revolution was in the nineth. These electronic media are not just limited to modern nations;they have affected music cultures all over the globe. They have brought about changes to traditional music instruments. According to the author, music notation is important because__________.