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The ''meter'' (or ''metre'') of music is its rhythmic structure, the patterns of accents heard in regularly recurring measures of stressed and unstressed beats (''arsis'' and ''thesis'') at the frequency of the music's pulse. A variety of systems exist throughout the world for organising and playing metrical music, such as the Indian system of ''tala'' and similar systems in Arabian and African music. Western music inherited the concept of metre from poetry (; ) where it denotes: the number of lines in a verse; the number of syllables in each line; and the arrangement of those syllables as long or short, accented or unaccented (; ). The first coherent system of rhythmic notation in modern Western music was based upon rhythmic modes derived from the basic types of metrical unit in the quantitative meter of classical ancient Greek and Latin poetry . Later music for dances such as the pavane and galliard consisted of musical phrases to accompany a fixed sequence of basic steps with a defined tempo and time signature. The English word "measure", originally an exact or just amount of time, came to denote either a poetic rhythm, a bar of music, or else an entire melodic verse or dance involving sequences of notes, words and/or movements that may last four, eight or sixteen bars. ==Metric structure== The term is not very precisely defined (). preferred to speak of "time" and "rhythmic shape", Imogen of "measured rhythm". However, London has written a book about musical metre, which "involves our initial perception as well as subsequent anticipation of a series of beats that we abstract from the rhythm surface of the music as it unfolds in time" (). This "perception" and "abstraction" of rhythmic measure is the foundation of human instinctive musical participation, as when we divide a series of identical clock-ticks into "tick-tock-tick-tock" (). "Rhythms of recurrence" arise from the interaction of two levels of motion, the faster providing the pulse and the slower organizing the beats into repetitive groups (). "Once a metric hierarchy has been established, we, as listeners, will maintain that organization as long as minimal evidence is present" (). A definition of musical meter requires the possibility of identifying a repeating pattern of accented pulses — a "pulse-group" — which corresponds to the foot in poetry. Frequently a pulse-group can be identified by taking the accented beat as the first pulse in the group and counting the pulses until the next accent (; ). Frequently meters can be broken down into a pattern of duples and triples (; ). The level of musical organisation implied by musical meter includes the most elementary levels of musical form (). Metrical rhythm, measured rhythm, and free rhythm are general classes of rhythm and may be distinguished in all aspects of temporality (). Metrical rhythm, by far the most common class in Western music, is where each time value is a multiple or fraction of a fixed unit (beat, see paragraph below), and normal accents re-occur regularly, providing systematic grouping (measures, divisive rhythm). Measured rhythm is where each time value is a multiple or fraction of a specified time unit but there are not regularly recurring accents (additive rhythm). Free rhythm is where there is neither (). Some music, including chant, has freer rhythm, like the rhythm of prose compared to that of verse (). Some music, such as some graphically scored works since the 1950s and non-European music such as Honkyoku repertoire for shakuhachi, may be considered ametric (). ''Senza misura'' is an Italian musical term for "without meter", meaning to play without a beat, using time to measure how long it will take to play the bar (). Metric structure includes meter, tempo, and all rhythmic aspects that produce temporal regularity or structure, against which the foreground details or durational patterns of any piece of music are projected (). Metric levels may be distinguished: the beat level is the metric level at which pulses are heard as the basic time unit of the piece. Faster levels are division levels, and slower levels are multiple levels (). A rhythmic unit is a durational pattern which occupies a period of time equivalent to a pulse or pulses on an underlying metric level. ==Frequently encountered types of meter== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Meter (music)」の詳細全文を読む スポンサード リンク
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