Material culture refers to the touchable, material 'things'—physical objects that can be seen, held, felt, used—that a culture produces. Examining a culture's tools and technology can tell us about the group's history and way of life. Similarly, research into the material culture of music can help us to understand the music culture. The most vivid body of 'thing' in it, 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-cultures in the remote past and their development. Here we have two kinds of evidence: instruments well preserved and instruments pictured in art. Through the study of instruments, as well as paintings, written documents, and so on, we can explore the movement of music from the Near East to China over a thousand years ago, for we can outline the spread of Near Eastern influence to Europe that resulted in the development of most of the instruments on the symphony orchestra. Sheet music or printed music, too, is material culture. Scholars once defined folk music-cultures as those in which people learn and sing music by ear rather than from print, but research shows mutual influence among oral and written sources during the past few centuries in Europe, Britain and America. Printed versions limit variety because they tend to standardize any song, yet they stimulate people to create new and different songs. Besides, the ability to read music notation has a far-reaching effect on musicians and, when it becomes widespread, on the music-culture as a whole. Music is deep-rooted in the cultural background that fosters it. We now pay more and more attention to traditional or ethnic features in folk music and are willing to preserve the fold music as we do with many traditional cultural heritage. Musicians all over the world are busy with recording classic music in their country for the sake of their unique culture. As always, people's aspiration will always focus on their individuality rather than universal features that are shared by all cultures alike. One more important part of music's material culture should be singled out: the influence of the electronic media—radio, record player, tape recorder, and television, 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 in the nineteenth. These electronic media are not just limited to modern nations they have affected music cultures all over the globe. Which of the following does not belong to material culture?