BEAT [Film Technology]

beat 
[Film Technology]

Variations in sound called beats, a consequence of the wave nature of sound, were discovered about 1740 by the Italian violinist Giuseppe Tartini and the German organist Georg Sorge. Most Western music is built on a structure of regularly recurring beats—that is, a metrical structure. This structure may be explicit (as in the beating of the bass drum in popular music and marching bands), or it may be implied (often in symphonic or instrumental music). Most Western music is built on a structure of regularly recurring beats—that is, a metrical structure. This structure may be explicit (as in the beating of the bass drum in popular music and marching bands), or it may be implied (often in symphonic or instrumental music). The three most common metres in Western music are units of four beats (with main stress on the first beat, secondary stress on the third beat); of three beats (stress on the first); and of six beats (primary stress on the first, secondary on the fourth). Conventionally, these metres are called , , and . Far greater complexity is found, however, in 20th-century Western art music, Indian classical music, and West African drum ensembles. Furthermore, much music is structured without regular metre, as in some genres in India and the Middle East, and in Christian, Jewish, Islamic, and Buddhist liturgical chant. Like the rhythms in nature, such as the motion of the planets, the succession of seasons, and the beating of the heart, musical rhythm is usually organized in regularly recurring patterns. Such patterns regulate the motion of the music and aid the human ear in grasping its structure. The most basic rhythmic unit is the beat or pulse—an evenly spaced pattern that resembles the ticking of a clock. In most dance and popular music, the pulse is explicitly stated, often by drumbeats or by a regular accompaniment pattern. In more complex music, the beat is often only implicit—a kind of common denominator for the actual lengths of the notes, which may be longer or shorter than the pulse itself. (When the listener taps a foot to such music, however, the pulse again becomes explicit.) For the pulse to be heard as a common denominator, the lengths of the individual notes must generally be its exact multiples or subdivisions (such as half the length of the pulse, or twice its length). The tempo of the music determines the speed of the beat. Just as the beats regulate the durations of such short musical events as a note or a pair of notes, the beats themselves are regulated by larger recurring units called bars. Bars are formed by stressing the first in a series of two or more beats, so that the beats group themselves into a pattern, for example; ONE two, ONE two, or ONE two three, ONE two three. (The first beat of the bar, which is the strongest, is called the downbeat; the last beat, the weakest, is called the upbeat.) The term metre can refer, first, to this general process of regular accentuation, and second, to the particular metrical grouping used in a given piece. In musical notation, metre is indicated by the time signature. When modern time signatures became established, the semibreve was regarded as the fundamental note value, and so they are expressed as the length of the bar in relation to the semibreve, which is given the value 1. The lower number in a time signature represents a note value expressed as a fraction of a semibreve; the upper number shows how many units of that note value there are in each bar. Thus, one of the most common time signatures, , effectively means “four quarters”: the unit of the bar is a quarter of a semibreve (i.e. a crotchet), and there are four such quarters in each bar. The time signatures , , and  all therefore represent the same rhythmic value per bar: the difference is in the number of beats and the pattern of stresses.  represents two beats per bar, with one stress (on the first beat), while  indicates four beats per bar with two stresses (strong on the first beat, weaker on the third). Metres such as  and  are called compound metres, because each rhythmic grouping in the bar is made of a sub-grouping of smaller rhythmic values.  represents two groups of three notes each,  three groups of three notes each etc. Metrically organized music is highly structured and tends to be regular. Once the metre is established, however, it need not be rigidly adhered to at all times; the listener's mind will retain the pattern even if the music temporarily contradicts it. Thus, a normally weak beat can be stressed, producing a syncopation (an accent that works against the prevailing metre). Conversely, a strong beat may occasionally be suppressed completely. Indeed, in complex metrical music a degree of tension always exists between, on the one hand, the metre as an abstract system of regulation and, on the other hand, the rhythmic flow of the actual note lengths—a flow that at times supports the metre and at other times does not. Furthermore, the pulse need not necessarily be maintained with absolute rigidity; it may be played rubato, that is, with variations so slight that they do not destroy the basic value.

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