MusicBroadly speaking, music is the artful or entertaining arrangement of sound and silence. The actual definition of music is hotly contested, and sounds accepted as music vary according to historical era and culture, but it is usually held that the sounds must at least be consciously organized, either by an individual or a group. Most music is made up, at least in part, of musical notes with definite pitches. Different notes played one at a time constitute a melody, while notes played at the same time make chords and harmony. Unpitched notes are often provided by percussion. The temporal organisation of these elements is rhythm. Music is extremely time related, not only in beats and rhythm but also in frequency and frequency patterns and harmonics. Some of these harmonic patterns are named "upper and lower harmonics". Humans usually enjoy music or sounds with "even order" harmonics in the like the sound of a bell, and tend to dislike music and sounds with "odd or random order" harmonics, like hitting a cardboard box with a flyswatter, however this is not always the case, and all harmony may be pleasant to someone. Also a musical song can associate a very old memory or a recent time to very specific date, sometimes when no other method of memory recall can. Music can be written in advance of a performance by a composer or songwriter. In such cases, the musician or musicians playing the piece (who may or may not also be the people who wrote it) broadly follow the instructions the composer has given them, which may be written down using musical notation in the form of sheet music. Alternatively, the music may be more-or-less made up by the performers as they go along (improvisation). Music can be performed by a single musician, or several may band together to form a musical ensemble such as a rock band or orchestra. The music they make can be heard through several media; the most traditional way is to hear it live, in the presence of the musicians. Live music can also be broadcast over the radio or television, although this experience is closer to playing back a sound recording or watching a music video. Sometimes, live performances incorporate prerecorded sounds; for example, a DJ uses records for scratching. Of course, you can also create music yourself, by singing, playing a musical instrument, or composing. Modern beginners usually try the guitar or the piano as a first instrument. Deaf people can experience music by feeling the vibrations in their body; the most famous example of a deaf musician is the composer Ludwig van Beethoven, who composed many famous works even after he had completely lost his hearing. In more modern times, Evelyn Glennie, who has been deaf since the age of twelve, is a highly acclaimed percussionist. People take music lessons when they want to learn to play music. Musicology is a broad field charged with the historical and scientific study of music, including music theory and music history. Since music is an ancient art, an extremely large number of musical genres have evolved. Among the larger genres are classical music, popular music and folk music. The term world music is applied to a wide range of music with an "ethnic" element. Ethnomusicology is the study of these genres in an anthropological context.