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| [[File:jid_3_2_pluck_adu_dr220.mp3]] [[:File:jid_3_2_pluck_adu_dr220.mp3|sound sample]] | | #REDIRECT [[3/2]] |
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| The '''just perfect fifth''' is the largest [[superparticular]] [[Gallery_of_Just_Intervals|interval]], spanning the distance between the 2nd and 3rd harmonics. It has a frequency ratio of [[3/2|3:2]], with a size of approximately 701.955 cents. It is an interval with low [[harmonic entropy]], and therefore high consonance.
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| Variations of the [[Perfect_fifth|fifth]] (whether just or not) appear in most music of the world. On a harmonic instrument, the third harmonic is usually the loudest which is not an octave double of the fundamental. Treatment of the perfect fifth as consonant historically precedes treatment of the major third (see [[5/4|5:4]]) as consonant. 3:2 is the simple JI interval best approximated by [[12edo|12edo]], after the [[Octave|octave]].
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| Producing a chain of just perfect fifths yields Pythagorean tuning. Such a chain does not close at a circle, but continues infinitely. [[12edo]] is a system which flattens the perfect fifth by about 2 cents so that the circle close at 12 tones. Meanwhile, [[meantone]] temperaments are systems which flatten the perfect fifth such that the major third generated by four fifths upward be closer to 5:4 -- or, in the case of [[quarter-comma meantone]] (see [[31edo]]), identical.
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| Some better (compared to 12edo) approximations of the perfect fifth are [[29edo]], [[41edo]], [[53edo]]...
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| (see all at [http://oeis.org/A060528 The On-Line Encyclopedia of Integer Sequences (OEIS)]; also relevant are the [http://oeis.org/A005664 denominators of the convergents to log2(3)]).
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| In composition, the presence of perfect fifths can provide a "ground" upon which unusual intervals may be placed while still sounding structurally coherent. Systems excluding perfect fifths can thus sound more "xenharmonic".
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| ...see also [http://en.wikipedia.org/wiki/Perfect_fifth Perfect fifth on Wikipedia].
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| [[Category:3-limit]]
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| [[Category:3/2]]
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| [[Category:interval]]
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| [[Category:interval_name]]
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| [[Category:just]]
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| [[Category:ratio]]
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