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{{Infobox Interval
{{interwiki
| de =
| en =
| es =
| ja =
| ko =
| ro = 3/2 (ro)
}}
{{Infobox interval
| Name = just perfect fifth
| Name = just perfect fifth
| Color name = w5, wa 5th
| Color name = w5, wa 5th
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{{Wikipedia|Perfect fifth}}
{{Wikipedia|Perfect fifth}}


'''3/2''', the '''just perfect fifth''', is the second largest [[superparticular]] [[interval]], spanning the distance between the 2nd and 3rd harmonics. It is an interval with low [[harmonic entropy]], and therefore high consonance. In composition, the presence of perfect fifths can provide a "ground" upon which unusual intervals may be placed while still sounding structurally coherent. There are many other uses of 3/2, and thus, systems excluding perfect fifths can thus sound more "xenharmonic". On a harmonic instrument, the third harmonic is usually the loudest one that is not an octave double of the fundamental, with 3/2 itself being the [[octave reduced]] form of this interval. Variations of the perfect fifth (whether just or not) appear in most music of the world. Treatment of the perfect fifth as consonant historically precedes treatment of the major third—specifically [[5/4]]—as consonant. 3/2 is the simplest [[just intonation]] interval to be very well approximated by [[12edo]], after the [[octave]].
'''3/2''', the '''just perfect fifth''', is a very [[consonance|consonant]] interval, due to the numerator and denominator of its ratio being very small numbers. Only the [[2/1|octave]] and the [[3/1|tritave]] have smaller numbers.
 
== Properties ==
For harmonic [[timbre|timbres]], the loudest harmonics are usually the second and third ones (2/1 and 3/1). 3/2 is the interval between these two harmonics (which incidentally makes 3/2 [[superparticular]]). Thus 3/2 is easy to tune by ear, and it's easy to hear if it's mistuned.  
 
== Usage ==
Variations of the perfect fifth (whether [[just]] or tempered) appear in most [[Approaches to musical tuning|music of the world]]. [[Historical temperaments|Historically]], European music treated the perfect fifth as consonant long before it treated the major third—specifically [[5/4]]—as consonant. In the present day, the dominant tuning [[12edo]] approximates 3/2 very accurately.
 
A [[Chain of fifths|chain of just perfect fifths]] generates [[Pythagorean tuning]]. The chain continues indefinitely and theoretically never returns to the starting note. A chain that ends at seven notes generates the historically important [[Wikipedia:Diatonic scale #Iteration of the fifth|Pythagorean diatonic scale]]. This scale is also the 7 natural notes of all "pyth-spine" notations, in which all uninflected notes are pythogorean, such as [[HEJI]], [[Sagittal notation|Sagittal]], [[Ups and downs notation|ups and downs]], [[FJS]] and [[color notation]].


Producing a chain of just perfect fifths yields [[Pythagorean tuning]]. Since log<sub>2</sub>(3) is an irrational number, a chain of just fifths continues indefinitely and will never returns to the starting note in either direction. Nevertheless, even in xenharmonic circles, the common label "perfect" for this interval retains value in at least some of the [[moment of symmetry]] scales created by this tuning&mdash;specifically in the [[TAMNAMS]] system – due to it being an interval that can be thought of as a multiple of the period plus or minus 0 or 1 generators. An example of such a scale is the familiar [[Wikipedia:Diatonic scale #Iteration of the fifth|Pythagorean diatonic scale]].
Music using unusual intervals can be very disorienting. The presence of perfect fifths can provide a "ground" that make it less so. Some composers deliberately use tunings that lack fifths, to make their music sound more [[xenharmonic]].


Meanwhile, [[meantone]] temperaments flatten the perfect fifth such that the major third generated by four fifths upward be closer to 5/4&mdash;or, in the case of [[quarter-comma meantone]] (see also [[31edo]]), identical. In such systems, and in common practice theory, the perfect fifth consists of four diatonic semitones and three chromatic semitones. In [[12edo]], and hence in most discussions these days, this is simplified to seven semitones, which is fitting seeing as 12edo is a system which flattens the perfect fifth by about 2 cents so that the circle close at 12 tones. On the other hand, in 5-limit just intonation, the just perfect fifth consists of four just diatonic semitones of [[16/15]], three just chromatic semitones of [[25/24]], and two syntonic commas of [[81/80]].
=== In regular temperament theory ===
Because 3/2 is a very simple and concordant interval, it is still recognizable even when heavily tempered. Often it is tempered so that an octave-reduced stack of fourths or fifths approximates some other interval. Some examples:


There are also [[superpyth]] (or "superpythagorean") temperaments, which ''sharpen'' the fifth from just so that the interval generated by four fifths upwards is closer to 9/7 and the interval generated by three fifths downnward is closer to 7/6. This also means that intervals such as A&ndash;G or C&ndash;B&#x266D; approximate 7/4 instead of 9/5.
[[Meantone]] temperament flattens the fifth from just (to around 695 cents) such that the major third generated by stacking four fifths is closer to (or even identical to) 5/4. The minor 3rd generated by stacking three fourths is closer to 6/5.


Then there is the possibility of [[schismatic]] temperaments, which flatten the perfect fifth such that an approximated 5/4 is generated by stacking eight fifths downwards; however, without a notation system that properly accounts for the syntonic comma (such as [[ups and downs notation]] or [[Syntonic-Rastmic Subchroma notation]]), the 5/4 will be invariably classified as a diminished fourth due to being enharmonic with [[8192/6561]], and this in turn results in common chords such as conventional [[Wikipedia: Major chord|Major]] and [[Wikipedia: Minor chord|Minor]] triads being awkward to notate.
[[Superpyth]] temperaments ''sharpen'' the fifth from just so that the major third is closer to 9/7 and the minor third is closer to 7/6. Thus the minor 7th 16/9 approximates 7/4 instead of 9/5.


Some tunings which have better (in terms of closeness to just intonation) approximations of the perfect fifth than in 12edo are [[29edo]], [[41edo]], and [[53edo]]. Of the aforementioned systems, 53edo is particularly noteworthy in regards to [[telicity]] as while 12edo is a 2-strong 3-2 telic system, 53edo is a 3-strong 3-2 telic system.
* One may choose to prioritize the accurate tuning of either the thirds or the harmonic seventh, leading to a ~710c tuning when prioritizing the thirds, or a ~715c tuning when prioritizing 7/4.
 
[[Schismatic|Schismic]] temperament adjusts the fifth such that the ''diminished'' fourth generated by stacking eight fourths approximates 5/4. As this is already a close approximation, the tuning of the fifth can be varied around its just tuning, but is most simply flattened by a tiny amount. Thus a triad with 5/4 is written as {{nowrap|{{dash|C, F♭, G}}}} (unless the notation has accidentals for [[81/80]], e.g. {{nowrap|{{dash|C, vE, G}}}}).
 
* Garibaldi temperament is an extension of schismatic that sharpens the fifth so that the small interval between the major third and diminished fourth can also be used to create simple 7-limit intervals.


== Approximations by edos ==
== Approximations by edos ==
The following [[edo]]s (up to 200) contain good approximations<ref>error magnitude below 7, both, absolute (in ¢) and relative (in r¢)</ref> of the interval 3/2. Errors are given by magnitude, the arrows in the table show if the edo representation is sharp (&uarr;) or flat (&darr;).
12edo approximates 3/2 to within only 2{{c}}. [[29edo]], [[41edo]], and [[53edo]] are even more accurate. In regards to [[telicity]], while 12edo is a 2-strong 3-2 [[telic]] system, 53edo is notably a 3-strong 3-2 telic system.
 
The following edos (up to 200) approximate 3/2 to within both 7{{c}} and 7%. Errors are unsigned so that the table can be sorted by them. The arrow column indicates a sharp (&uarr;) or flat (&darr;) fifth.


{| class="wikitable sortable right-1 center-2 right-3 right-4 center-5"
{| class="wikitable sortable right-1 center-2 right-3 right-4 center-5"
|-
|-
! [[Edo]]
! [[Edo]]
! class="unsortable" | deg\edo
! class="unsortable" | Deg\edo
! Absolute<br>Error ([[Cent|¢]])
! Absolute <br>error ([[Cent|¢]])
! Relative<br>Error ([[Relative cent|r¢]])
! Relative <br>error (%)
! &#8597;
! &#x2195;
! class="unsortable" | Equally acceptable multiples <ref>Super-edos up to 200 within the same error tolerance</ref>
! class="unsortable" | Equally accurate <br>multiples
|-
|-
|  [[12edo|12]]  ||  7\12  || 1.9550 || 1.9550 || &darr; || [[24edo|14\24]], [[36edo|21\36]]
|  [[12edo|12]]  ||  7\12  || 1.955 || 1.955 || &darr; || [[24edo|14\24]], [[36edo|21\36]]
|-
|-
|  [[17edo|17]]  ||  10\17  || 3.9274 || 5.5637 || &uarr; ||  
|  [[17edo|17]]  ||  10\17  || 3.927 || 5.564 || &uarr; ||  
|-
|-
|  [[29edo|29]]  ||  17\29  || 1.4933 || 3.6087 || &uarr; ||  
|  [[29edo|29]]  ||  17\29  || 1.493 || 3.609 || &uarr; ||  
|-
|-
|  [[41edo|41]]  ||  24\41  || 0.4840 || 1.6537 || &uarr; || [[82edo|48\82]], [[123edo|72\123]], [[164edo|96\164]]
|  [[41edo|41]]  ||  24\41  || 0.484 || 1.654 || &uarr; || [[82edo|48\82]], [[123edo|72\123]], [[164edo|96\164]]
|-
|-
|  [[53edo|53]]  ||  31\53  || 0.0682 || 0.3013 || &darr; || [[106edo|62\106]], [[159edo|93\159]]
|  [[53edo|53]]  ||  31\53  || 0.068 || 0.301 || &darr; || [[106edo|62\106]], [[159edo|93\159]]
|-
|-
|  [[65edo|65]]  ||  38\65  || 0.4165 || 2.2563 || &darr; || [[130edo|76\130]], [[195edo|114\195]]
|  [[65edo|65]]  ||  38\65  || 0.416 || 2.256 || &darr; || [[130edo|76\130]], [[195edo|114\195]]
|-
|-
|  [[70edo|70]]  ||  41\70  || 0.9021 || 5.2625 || &uarr; ||  
|  [[70edo|70]]  ||  41\70  || 0.902 || 5.262 || &uarr; ||  
|-
|-
|  [[77edo|77]]  ||  45\77  || 0.6563 || 4.2113 || &darr; ||  
|  [[77edo|77]]  ||  45\77  || 0.656 || 4.211 || &darr; ||  
|-
|-
|  [[89edo|89]]  ||  52\89  || 0.8314 || 6.1663 || &darr; ||  
|  [[89edo|89]]  ||  52\89  || 0.831 || 6.166 || &darr; ||  
|-
|-
|  [[94edo|94]]  ||  55\94  || 0.1727 || 1.3525 || &uarr; || [[188edo|110\188]]
|  [[94edo|94]]  ||  55\94  || 0.173 || 1.352 || &uarr; || [[188edo|110\188]]
|-
|-
| [[111edo|111]] ||  65\111 || 0.7477 || 6.9162 || &uarr; ||  
| [[111edo|111]] ||  65\111 || 0.748 || 6.916 || &uarr; ||  
|-
|-
| [[118edo|118]] ||  69\118 || 0.2601 || 2.5575 || &darr; ||  
| [[118edo|118]] ||  69\118 || 0.260 || 2.557 || &darr; ||  
|-
|-
| [[135edo|135]] ||  79\135 || 0.2672 || 3.0062 || &uarr; ||  
| [[135edo|135]] ||  79\135 || 0.267 || 3.006 ||&uarr; ||  
|-
|-
| [[142edo|142]] ||  83\142 || 0.5466 || 6.4675 || &darr; ||  
| [[142edo|142]] ||  83\142 || 0.547 || 6.467 || &darr; ||  
|-
|-
| [[147edo|147]] ||  86\147 || 0.0858 || 1.0512 || &uarr; ||  
| [[147edo|147]] ||  86\147 || 0.086 || 1.051 || &uarr; ||  
|-
|-
| [[171edo|171]] || 100\171 || 0.2006 || 2.8588 || &darr; ||  
| [[171edo|171]] || 100\171 || 0.200 || 2.859 || &darr; ||  
|-
|-
| [[176edo|176]] || 103\176 || 0.3177 || 4.6600 || &uarr; ||  
| [[176edo|176]] || 103\176 || 0.318 || 4.660 || &uarr; ||  
|-
|-
| [[183edo|183]] || 107\183 || 0.3157 || 4.8138 || &darr; ||  
| [[183edo|183]] || 107\183 || 0.316 || 4.814 || &darr; ||  
|-
|-
| [[200edo|200]] || 117\200 || 0.0450 || 0.7500 || &uarr; ||  
| [[200edo|200]] || 117\200 || 0.045 || 0.750 || &uarr; ||  
|}
|}


<references/>
Edos can be classified by their approximation of 3/2 as:
* '''Superflat''' edos have fifths narrower than {{nowrap|4\7 {{=}} ~686{{c}}}}
* '''Perfect''' edos have fifths of exactly 4\7
* '''Diatonic''' edos have fifths between 4\7 and {{nowrap|3\5 {{=}} 720{{c}}}}
* '''Pentatonic''' have fifths of exactly 3\5
* '''Supersharp''' edos have fifths wider than 3\5
 
{| class="wikitable sortable"
{| class="wikitable sortable"
|+ Comparison of edo approximations of 3/2 and "fifth classes" (from 5edo to 31edo)
|+ style="font-size: 105%;" | Comparison of the fifths of edos 5 to 31
|-
! Edo
! Edo
! Degree
! Degree
! Cents
! Cents
! Fifth Category
! Edo Category
! Error (¢)
! Error (¢)
|-
|-
Line 81: Line 111:
| 3\5
| 3\5
| 720.000
| 720.000
| pentatonic edo
| Pentatonic edo
| +18.045
| +18.045
|-
|-
| [[7edo]]
| [[7edo]]
Line 88: Line 118:
| 685.714
| 685.714
| perfect edo
| perfect edo
| -16.241
| −16.241
|-
|-
| [[8edo]]
| [[8edo]]
Line 94: Line 124:
| 750.000
| 750.000
| supersharp edo
| supersharp edo
| +48.045
| +48.045
|-
|-
| [[9edo]]
| [[9edo]]
Line 100: Line 130:
| 666.667
| 666.667
| superflat edo
| superflat edo
| -35.288
| −35.288
|-
|-
| [[10edo]]
| [[10edo]]
Line 106: Line 136:
| 720.000
| 720.000
| pentatonic edo
| pentatonic edo
| +18.045
| +18.045
|-
|-
| [[11edo]]
| [[11edo]]
Line 112: Line 142:
| 654.545
| 654.545
| superflat edo
| superflat edo
| -47.41
| −47.41
|-
|-
| [[12edo]]
| [[12edo]]
Line 118: Line 148:
| 700.000
| 700.000
| diatonic edo
| diatonic edo
| -1.955
| −1.955
|-
|-
| [[13edo]]
| [[13edo]]
Line 124: Line 154:
| 738.462
| 738.462
| supersharp edo
| supersharp edo
| +36.507
| +36.507
|-
|-
| [[14edo]]
| [[14edo]]
Line 130: Line 160:
| 685.714
| 685.714
| perfect edo
| perfect edo
| -16.241
| −16.241
|-
|-
| [[15edo]]
| [[15edo]]
Line 136: Line 166:
| 720.000
| 720.000
| pentatonic edo
| pentatonic edo
| +18.045
| +18.045
|-
|-
| [[16edo]]
| [[16edo]]
Line 142: Line 172:
| 675.000
| 675.000
| superflat edo
| superflat edo
| -26.955
| −26.955
|-
|-
| [[17edo]]
| [[17edo]]
Line 148: Line 178:
| 705.882
| 705.882
| diatonic edo
| diatonic edo
| +3.927
| +3.927
|-
|-
| [[18edo]]
| [[18edo]]
Line 154: Line 184:
| 733.333
| 733.333
| supersharp edo
| supersharp edo
| +31.378
| +31.378
|-
|-
| [[19edo]]
| [[19edo]]
Line 160: Line 190:
| 694.737
| 694.737
| diatonic edo
| diatonic edo
| -7.218
| −7.218
|-
|-
| [[20edo]]
| [[20edo]]
Line 166: Line 196:
| 720.000
| 720.000
| pentatonic edo
| pentatonic edo
| +18.045
| +18.045
|-
|-
| [[21edo]]
| [[21edo]]
Line 172: Line 202:
| 685.714
| 685.714
| perfect edo
| perfect edo
| -16.241
| −16.241
|-
|-
| [[22edo]]
| [[22edo]]
Line 178: Line 208:
| 709.091
| 709.091
| diatonic edo
| diatonic edo
| +7.136
| +7.136
|-
|-
| [[23edo]]
| [[23edo]]
Line 184: Line 214:
| 678.261
| 678.261
| superflat edo
| superflat edo
| -23.694
| −23.694
|-
|-
| [[24edo]]
| [[24edo]]
Line 190: Line 220:
| 700.000
| 700.000
| diatonic edo
| diatonic edo
| -1.955
| −1.955
|-
|-
| [[25edo]]
| [[25edo]]
Line 196: Line 226:
| 720.000
| 720.000
| pentatonic edo
| pentatonic edo
| +18.045
| +18.045
|-
|-
| [[26edo]]
| [[26edo]]
Line 202: Line 232:
| 692.308
| 692.308
| diatonic edo
| diatonic edo
| -9.647
| −9.647
|-
|-
| [[27edo]]
| [[27edo]]
Line 208: Line 238:
| 711.111
| 711.111
| diatonic edo
| diatonic edo
| +9.156
| +9.156
|-
|-
| [[28edo]]
| [[28edo]]
Line 214: Line 244:
| 685.714
| 685.714
| perfect edo
| perfect edo
| -16.241
| −16.241
|-
|-
| [[29edo]]
| [[29edo]]
Line 220: Line 250:
| 703.448
| 703.448
| diatonic edo
| diatonic edo
| +1.493
| +1.493
|-
|-
| [[30edo]]
| [[30edo]]
| 17\30
| 18\30
| 720.000
| 720.000
| pentatonic edo
| pentatonic edo
| +18.045
| +18.045
|-
|-
| [[31edo]]
| [[31edo]]
Line 232: Line 262:
| 696.774
| 696.774
| diatonic edo
| diatonic edo
| -5.181
| −5.181
|}
|}
* The many and various 3/2 approximations in different edos can be classified as (after [[Kite Giedraitis]]):
** '''Superflat''' edos have fifths narrower than 686 cents.
** '''Perfect''' or '''heptatonic''' edos have fifths 685{{frac|4|7}} cents wide (and 4/7 steps).
** '''Diatonic''' edos have fifths between 685{{frac|4|7}} and 720 cents wide.
** '''Pentatonic''' have fifths exactly 720 cents wide.
** '''Supersharp''' edos have fifths wider than 720 cents.


== See also ==
== See also ==
* [[4/3]] – its [[octave complement]]
* [[4/3]] – its [[octave complement]]
* [[Fifth complement]]
* [[Fifth complement]]
* [[Edf]]
* [[Edf]] – tunings which equally divide 3/2
* [[Gallery of just intervals]]
* [[Gallery of just intervals]]
* {{OEIS| A060528 }} – sequence of edos with increasingly better approximations of 3/2 (and by extension 4/3)
* {{OEIS| A060528 }} – sequence of edos with increasingly better approximations of 3/2 (and by extension 4/3)
Retrieved from "https://en.xen.wiki/w/3/2"