Editing Metre (music) (section)

==Polymetre==
{{anchor|Polymeter}}
{{see also|Polyrhythm}}

With polymetre, the bar sizes differ, but the beat remains constant. Since the beat is the same, the various metres eventually agree. (Four bars of {{music|time|7|4}} = seven bars of {{music|time|4|4}}). An example is the second moment, titled "Scherzo polimetrico", of [[Edmund Rubbra]]'s Second String Quartet (1951), in which a constant triplet texture holds together overlapping bars of {{music|time|9|8}}, {{music|time|12|8}}, and {{music|time|21|8}}, and barlines rarely coincide in all four instruments.{{sfn|Rubbra|1953|loc=41}}

With [[polyrhythm]], the number of beats varies within a fixed bar length. For example, in a 4:3 polyrhythm, one part plays {{music|time|4|4}} while the other plays {{music|time|3|4}}, but the {{music|time|3|4}} beats are stretched so that three beats of {{music|time|3|4}} are played in the same time as four beats of {{music|time|4|4}}.{{cn|date=October 2020}} More generally, sometimes rhythms are combined in a way that is neither tactus nor bar preserving—the beat differs and the bar size also differs. See [[Polytempo|Polytempi]].{{cn|date=October 2020}}

Research into the perception of polymetre shows that listeners often either extract a [[composite rhythm|composite]] pattern that is fitted to a metric framework, or focus on one rhythmic stream while treating others as "noise". This is consistent with the [[Gestalt psychology]] tenet that "the [[figure-ground (perception)|figure–ground]] dichotomy is fundamental to all perception".{{sfn|Boring|1942|loc=253}}{{vn|date=August 2013}}{{sfn|London|2004|loc=49–50}} In the music, the two metres will meet each other after a specific number of beats. For example, a {{music|time|3|4}} metre and {{music|time|4|4}} metre will meet after 12 beats.

<!--This paragraph is in danger of becoming a trivia list. There are hundreds, possibly thousands of popular-music bands who have used polyrhythm. Please think twice before adding more.-->In "Toads of the Short Forest" (from the album ''[[Weasels Ripped My Flesh]]''), composer [[Frank Zappa]] explains: "At this very moment on stage we have drummer A playing in {{music|time|7|8}}, drummer B playing in {{music|time|3|4}}, the bass playing in {{music|time|3|4}}, the organ playing in {{music|time|5|8}}, the tambourine playing in {{music|time|3|4}},{{Clarify|date=June 2015}}<!--How can this be describing a common beat with different-length bars? surely the players in {{music|time|7|8}} and {{music|time|5|8}} metres must be using a different counting unit from the ones in {{music|time|3|4}}.--> and the alto sax blowing his nose".{{sfn|Mothers of Invention|1970}} "Touch And Go", a [[The Cars discography|hit single]] by [[The Cars]], has polymetric verses, with the drums and bass playing in {{music|time|5|4}}, while the guitar, synthesizer, and vocals are in {{music|time|4|4}} (the choruses are entirely in {{music|time|4|4}}).{{sfn|Cars|1981|loc=15}} [[Magma (band)|Magma]] uses extensively {{music|time|7|8}} on {{music|time|2|4}} (e.g. [[Mëkanïk Dëstruktïẁ Kömmandöh]]) and some other combinations. [[King Crimson]]'s albums of the eighties have several songs that use polymetre of various combinations.{{cn|date=October 2020}}

Polymetres are a defining characteristic of the music of [[Meshuggah]], whose compositions often feature unconventionally timed rhythm figures cycling over a {{music|time|4|4}} base.{{sfn|Pieslak|2007}}

===Examples===
{|
|+Polymetres
| [[File:Polymeter-5c4.ogv|thumb|none|133px|Beat-preserving polymetre {{music|time|5|4}} with {{music|time|4|4}}]]
| [[File:Polymeter-5c3.ogv|thumb|none|133px|Beat-preserving polymetre {{music|time|5|4}} with {{music|time|3|4}}]]
| [[File:Polymeter-3c4.theora.ogv|thumb|none|133px|Measure-preserving polyrhythm {{music|time|3|4}} with {{music|time|4|4}}]]
|-
| [[File:Polymeter-2o4c3o8.ogv|thumb|none|133px|Beat-preserving polymetre {{music|time|2|4}} with {{music|time|3|8}}]]
| [[File:Polymeter-4o4c5o8.ogv|thumb|none|133px|Beat-preserving polymetre {{music|time|4|4}} with {{music|time|5|8}}]]
| [[File:Polymeter-4o4c7o8.ogv|thumb|none|133px|Beat-preserving polymetre {{music|time|4|4}} with {{music|time|7|8}}]]
|-
|[[File:Polyrhythm3c2.theora.ogv|thumb|none|133px|Measure-preserving polyrhythm 2:3]]
| [[File:Polyrhythm4c3.theora.ogv|thumb|none|133px|Measure-preserving polyrhythm 4:3]]
| [[File:Polyrhythm-5 o 4 with 4 o 4 simultaneously.ogv|thumb|none|133px|Measure-preserving polyrhythm 5:4]]
|}

{|
|+Various metres
| [[File:Video of 6o8 at 90 bpm.ogv|thumb|none|133px|{{music|time|6|8}} at tempo of 90&nbsp;bpm]]
| [[File:Video for 9o8 at 90 bpm.ogv|thumb|none|133px|{{music|time|9|8}} at tempo of 90&nbsp;bpm]]
| [[File:Video for 12o8 at 90 bpm.ogv|thumb|none|133px|{{music|time|12|8}} at tempo of 90&nbsp;bpm]]
|-
| [[File:Video for 2o4 at 60 bpm.ogv|thumb|none|133px|{{music|time|2|4}} at a tempo of 60&nbsp;bpm]]
| [[File:Video for 3o4 at 60 bpm.ogv|thumb|none|133px|{{music|time|3|4}} at a tempo of 60&nbsp;bpm]]
| [[File:Video for 4o4 at 60 bpm.ogv|thumb|none|133px|{{music|time|4|4}} at a tempo of 60&nbsp;bpm]]
|}