15/13: Difference between revisions

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**Imported revision 513214962 - Original comment: **
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Semifourth and other things
 
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<h2>IMPORTED REVISION FROM WIKISPACES</h2>
{{Infobox Interval
This is an imported revision from Wikispaces. The revision metadata is included below for reference:<br>
| Name = tridecimal semifourth
: This revision was by author [[User:spt3125|spt3125]] and made on <tt>2014-06-07 23:11:59 UTC</tt>.<br>
| Color name = 3uy2, thuyo 2nd
: The original revision id was <tt>513214962</tt>.<br>
| Sound = jid_15_13_pluck_adu_dr220.mp3
: The revision comment was: <tt></tt><br>
}}
The revision contents are below, presented both in the original Wikispaces Wikitext format, and in HTML exactly as Wikispaces rendered it.<br>
In [[13-limit]] [[just intonation]], '''15/13''', the '''tridecimal semifourth''' is an interval measuring about 247.7¢, wherein two instances of this fall short of [[4/3]] by [[676/675]].
<h4>Original Wikitext content:</h4>
<div style="width:100%; max-height:400pt; overflow:auto; background-color:#f8f9fa; border: 1px solid #eaecf0; padding:0em"><pre style="margin:0px;border:none;background:none;word-wrap:break-word;white-space: pre-wrap ! important" class="old-revision-html">**15/13**
|0 1 1 0 0 -1&gt;
247.74105 cents
[[media type="file" key="jid_15_13_pluck_adu_dr220.mp3"]] [[file:xenharmonic/jid_15_13_pluck_adu_dr220.mp3|sound sample]]


In [[13-limit]] [[Just Intonation]], 15/13 is an interval measuring about 247.7¢. In the language of [[Margo Schulter]], 15/13 is an instance of an [[interseptimal]] interval, as it falls in an ambiguous zone between two septimal extremes -- namely the large minor second [[8_7|8/7]] and the small minor third [[7_6|7/6]]. (15/13)*([[13_10|13/10]])=[[3_2|3/2]], which implies that 15/13 and 13/10 make a 3/2 perfect fifth. Thus you can make a [[List of root-3rd-P5 triads in JI|root-3rd-P5]] triad that goes 26:30:39, with a 15/13 "inframinor third" up from the root.
In the language of [[Margo Schulter]], 15/13 is an instance of an [[interseptimal]] interval, as it falls in an ambiguous zone between two septimal extremes namely the large major second [[8/7]] and the small minor third [[7/6]]. (15/13)×([[13/10]]) = [[3/2]], which implies that 15/13 and 13/10 make a 3/2 perfect fifth. Thus you can make a [[List of root-3rd-P5 triads in JI|root-3rd-P5]] triad that goes 26:30:39, with a 15/13 ''inframinor third'' up from the root.


See: [[Gallery of Just Intervals]], [[The Archipelago]]</pre></div>
When being used as type of second, it is given the name ''ultramajor second'' as it is even sharper than 8/7 which is often called a "supermajor second". In extended [[Pythagorean tuning]] it is extremely close to {{Monzo|43 -27}}.
<h4>Original HTML content:</h4>
 
<div style="width:100%; max-height:400pt; overflow:auto; background-color:#f8f9fa; border: 1px solid #eaecf0; padding:0em"><pre style="margin:0px;border:none;background:none;word-wrap:break-word;width:200%;white-space: pre-wrap ! important" class="old-revision-html">&lt;html&gt;&lt;head&gt;&lt;title&gt;15_13&lt;/title&gt;&lt;/head&gt;&lt;body&gt;&lt;strong&gt;15/13&lt;/strong&gt;&lt;br /&gt;
== Approximation ==
|0 1 1 0 0 -1&amp;gt;&lt;br /&gt;
{{Interval edo approximation|15/13}}
247.74105 cents&lt;br /&gt;
== See also ==
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* [[26/15]] – its [[octave complement]]
&lt;br /&gt;
* [[13/10]] – its [[fifth complement]]
In &lt;a class="wiki_link" href="/13-limit"&gt;13-limit&lt;/a&gt; &lt;a class="wiki_link" href="/Just%20Intonation"&gt;Just Intonation&lt;/a&gt;, 15/13 is an interval measuring about 247.7¢. In the language of &lt;a class="wiki_link" href="/Margo%20Schulter"&gt;Margo Schulter&lt;/a&gt;, 15/13 is an instance of an &lt;a class="wiki_link" href="/interseptimal"&gt;interseptimal&lt;/a&gt; interval, as it falls in an ambiguous zone between two septimal extremes -- namely the large minor second &lt;a class="wiki_link" href="/8_7"&gt;8/7&lt;/a&gt; and the small minor third &lt;a class="wiki_link" href="/7_6"&gt;7/6&lt;/a&gt;. (15/13)*(&lt;a class="wiki_link" href="/13_10"&gt;13/10&lt;/a&gt;)=&lt;a class="wiki_link" href="/3_2"&gt;3/2&lt;/a&gt;, which implies that 15/13 and 13/10 make a 3/2 perfect fifth. Thus you can make a &lt;a class="wiki_link" href="/List%20of%20root-3rd-P5%20triads%20in%20JI"&gt;root-3rd-P5&lt;/a&gt; triad that goes 26:30:39, with a 15/13 &amp;quot;inframinor third&amp;quot; up from the root.&lt;br /&gt;
* [[Gallery of just intervals]]
&lt;br /&gt;
* [[The Archipelago]]
See: &lt;a class="wiki_link" href="/Gallery%20of%20Just%20Intervals"&gt;Gallery of Just Intervals&lt;/a&gt;, &lt;a class="wiki_link" href="/The%20Archipelago"&gt;The Archipelago&lt;/a&gt;&lt;/body&gt;&lt;/html&gt;</pre></div>
 
[[Category:Interseptimal intervals]]
[[Category:Semifourth]]
[[Category:Third]]
[[Category:Subminor third]]
[[Category:Second]]
[[Category:Supermajor second]]

Latest revision as of 18:59, 10 April 2026

Interval information
Ratio 15/13
Factorization 3 × 5 × 13-1
Monzo [0 1 1 0 0 -1
Size in cents 247.7411¢
Name tridecimal semifourth
Color name 3uy2, thuyo 2nd
FJS name [math]\displaystyle{ \text{A2}^{5}_{13} }[/math]
Special properties reduced
Tenney norm (log2 nd) 7.60733
Weil norm (log2 max(n, d)) 7.81378
Wilson norm (sopfr(nd)) 21

[sound info]
Open this interval in xen-calc

In 13-limit just intonation, 15/13, the tridecimal semifourth is an interval measuring about 247.7¢, wherein two instances of this fall short of 4/3 by 676/675.

In the language of Margo Schulter, 15/13 is an instance of an interseptimal interval, as it falls in an ambiguous zone between two septimal extremes – namely the large major second 8/7 and the small minor third 7/6. (15/13)×(13/10) = 3/2, which implies that 15/13 and 13/10 make a 3/2 perfect fifth. Thus you can make a root-3rd-P5 triad that goes 26:30:39, with a 15/13 inframinor third up from the root.

When being used as type of second, it is given the name ultramajor second as it is even sharper than 8/7 which is often called a "supermajor second". In extended Pythagorean tuning it is extremely close to [43 -27.

Approximation

Edo approximations for 15/13 (247.74 ¢)
≤ 80edo, relative error ≤ 10%
Edo Step size Cents (¢) Absolute error (¢) Relative error (%)
5 1\5 240.00 -7.74 -3.23
10 2\10 240.00 -7.74 -6.45
15 3\15 240.00 -7.74 -9.68
19 4\19 252.63 +4.89 +7.74
24 5\24 250.00 +2.26 +4.52
29 6\29 248.28 +0.53 +1.29
34 7\34 247.06 -0.68 -1.93
39 8\39 246.15 -1.59 -5.16
44 9\44 245.45 -2.29 -8.38
48 10\48 250.00 +2.26 +9.04
53 11\53 249.06 +1.32 +5.81
58 12\58 248.28 +0.53 +2.58
63 13\63 247.62 -0.12 -0.64
68 14\68 247.06 -0.68 -3.87
73 15\73 246.58 -1.17 -7.09

See also