Music
    
    Music, the organized movement of sounds through a continuum of time. Music plays a role in all societies, and it exists in a large number of styles, each characteristic of a geographical region or a historical era.
    Cultural Definitions
    All known societies have music, but only a few languages have a specific word for it. In Western culture, dictionaries usually define music as an art that is concerned with combining sounds-particularly pitches-to produce an artifact that has beauty or attractiveness, that expresses something, that follows some kind of internal logic and exhibits intelligible structure, and that requires special skill on the part of its creator. Clearly, music is not easy to define, and yet most people recognize the concept of music and generally agree on whether or not a given sound is musical.
    Indefinite border areas exist, however, between music and other sound phenomena such as speech, and the cultures of the world differ in their opinion of the musicality of various sounds. Thus, simple tribal chants, a half-spoken style of singing, or a composition created by a computer program may or may not be accepted as music by members of a given society or subgroup. Muslims, for example, do not consider the chanting of the Koran to be a kind of music, although the structure of the chant is similar to that of secular singing. The social context of sounds may determine whether or not they are regarded as music. Industrial noises, for instance, are not music except when presented as part of a concert of experimental music in an auditorium, with a listed composer.
    Opinions also differ as to the origins and spiritual value of music. In some African cultures music is seen as something uniquely human; among some Native Americans it is thought to have originated as a way for spirits to communicate. In Western culture music is regarded as inherently good, and sounds that are welcome are said to be "music to the ears." In some other cultures-for example, Islamic culture-it is of low value, associated with sin and evil, and attempts have been made to outlaw its practice.
    Music as a Cultural System
    Music has many uses, and in all societies certain events are inconceivable without it. A proper consideration of music should involve the musical sound itself; but it should also deal with the concepts leading to its existence, with its particular forms and functions in each culture, and with the human behavior that produces the sound.
    Somewhat analogous to having a language, each society may be said to have "a music"-that is, a self-contained system within which musical communication takes place and that, like a language, must be learned to be understood. Members of some societies participate in several musics; thus, modern Native Americans take part in both traditional Native American music and mainstream American music.
    Within each music, various strata may exist, distinguished by degree of learning (professional versus untrained musicians), level of society (the music of the elite versus that of the masses), patronage (court or church or public commercial establishments), and manner of dissemination (oral, notated, or through mass media). In the West and in the high cultures of Asia, it is possible to distinguish three basic strata: first, "art" or "classical" music, composed and performed by trained professionals originally under the patronage of courts and religious establishments; second, folk music, shared by the population at large-particularly its rural component-and transmitted orally; and, third, popular music, performed by professionals, disseminated through radio, television, records, film, and print, and consumed by the urban mass public.
    The Sounds of Music
    
    In the simplest terms music can be described as the juxtaposition of two elements that involve pitch and duration and that are usually called melody and rhythm. The minimal unit of musical organization is the tone-that is, a sound with specific pitch and duration. Music thus consists of combinations of individual tones that appear successively (melody) or simultaneously (harmony) or, as in most Western music, both.
    Melody
    In any musical system, the creation of melody involves selecting tones from a prescribed set called a scale, which is actually a group of pitches separated by specific intervals (the distances in pitch between tones). Thus, the scale of 18th- and 19th-century Western music is the chromatic scale, represented by the piano keyboard with its 12 equidistant tones per octave; composers selected from these tones to produce all their music. Much Western music is also based on diatonic scales-those with seven tones per octave, as illustrated by the white keys on the piano keyboard. In the diatonic scales and in the pentatonic scales-those with five tones per octave, most often corresponding to the black keys on the piano-that are common in folk music, the tones are not equidistant.
    Intervals can be measured in units called cents, 1200 per octave. The typical intervals of Western music are multiples of 100 cents, but in other musical cultures intervals of about 50, 150, and 240 cents, for example, are also found. The human ear can distinguish intervals as small as 14 cents, but no interval that small seems to play a significant role in any musical system.
    Rhythm
    
    The handling of time in music is expressed through concepts such as the lengths of notes and the interrelationships among them; relative degrees of emphasis on different tones; and, in particular, meter.
    Most Western music is built on a structure of regularly recurring beats-that is, a metrical structure. ............