Metre (music)

Metre ismeasurement ofmusical line into measuresstressedunstressed beats, indicatedWestern notation bysymbol calledtime signature. Properly, "metre" describeswhole conceptmeasuring rhythmic units, butcan also be used asspecific descriptor formeasurementan individual piece as represented bytime signature --example, "This piecein 4/4 metre"equivalent"This piecein 4/4 time" or "This piece has4/4 time signature."

A measure has two purposesWestern traditionsmusic,first isblock outseries beatss, andsecond isformbuilding blocklarger sectionsmusic, such asphrase. Time signatures imply strongly accented beats,others thatless accented, changing time signature changespatternemphasizing notes, either by playing certain notes louder, or by sustaining them asswing or rubato. A measuresimilar tometrical footpoetry (See Meter (poetry)).

Therefour different typesmetrecommon use: simple duple (ex. 4/4), simple triple (ex. 3/4), compound duple (ex. 6/8),compound triple (ex. 9/8). If each beat inmeasuredivided into two parts, itsimple meter,if divided into three itcompound. If each measuredivided into two beats, itduple meter,if three ittriple. Some people also label quadruple, while some consideras two duples. The lattermore consistent withabove labeling system, as any other division above triple, such as quintuple,considered as duple+triple (12123) or triple+duple (12312), depending onaccents inmusical example. However,some musicquintuple may be treatedperceived as one unitfive, especially at faster tempos.

Most popular musicin 4/4 time, though often may be2/2 or cut time such asbossa nova. Doo-wopsome other rock stylesfrequently12/8, or may be interpreted as 4/4heavy swing. Similarly, most classical music before20th century tendedstickrelatively straightforward metres such as 4/4, 3/46/8, though variations on these such as 3/26/4also found. By20th century, composers were using less regular metres, such as 5/47/8.

Also in20th century,became relatively more commonswitch metre frequently—the endIgor Stravinsky's The RiteSpring isparticularly extreme example—anduseasymmetrical rhythms where each beat isdifferent length became more common: such metres include already discussed quintuple rhythms as well as more complex constructs alonglines2+5+3/4 time, where each bar has2 beat unit,five beat unit and3 beat unit, withstress atbeginningeach unit—theresimilar metres usedvarious folk musics. Other music has no meter at all (free time) such as drone based music exemplified by La Monte Young, feature rhythms so complex that any metreobscured such asserialism, orbased on additive rhythms, such as some music by Philip Glass.

Metreoften combined withrhythmic patternproduceparticular style. Thistruedance music, such aswaltz or tango, which have particular patternsemphasizing beats whichinstantly recognizable. Thisoften donemakemusic coincideslow or fast steps indance,can be thoughtasmusical equivalentprosody.