4000/3969: Difference between revisions

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+ a commatic identity. - edos (octagar family page contains better sequences). - see also
 
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The '''octagar comma''' is a [[small comma|small]] [[7-limit]] [[comma]] with a [[ratio]] of 4000/3969. It is the difference between a stack of three [[10/9]]'s and a stack of two [[7/6]]'s. It is also the difference between [[50/49]] and [[81/80]], and is equal to ([[10/9]])/([[21/20]])<sup>2</sup>, with [[S-expression]] S19⋅S20<sup>2</sup>, making it a lopsided comma.  
The '''octagar comma''' is a [[small comma|small]] [[7-limit]] [[comma]] with a [[ratio]] of 4000/3969. It is the difference between a stack of three [[10/9]]s and a stack of two [[7/6]]s.


== Temperaments ==
== Temperaments ==
Tempering out this comma alone in the 7-limit leads to the [[octagar]] temperament. See [[Octagar family]] for the family of rank-3 temperaments where it is tempered out. See [[Octagar temperaments]] for a collection of rank-2 temperaments where it is tempered out.
[[Tempering out]] this comma alone in the 7-limit leads to the [[octagar]] temperament. See [[Octagar family]] for the family of rank-3 temperaments where it is tempered out. See [[Octagar temperaments]] for a collection of rank-2 temperaments where it is tempered out.
 
It is also tempered out in the following [[edo]]s (by [[simple map]]): {{EDOs|3, 12, 15, 23, 26, 27, 29, 30, 38, 41, 42, 53, 56, 68, 71, 79, 80, 82, 83, 94, 95, 97}}...


== Etymology ==
== Etymology ==
This comma was named as ''octagari'' by [[Gene Ward Smith]] in 2005 as a contraction of ''[[octacot]]'' and ''[[garibaldi]]''<ref>[https://yahootuninggroupsultimatebackup.github.io/tuning-math/topicId_12900.html Yahoo! Tuning Group | ''Seven limit comma names from pairs of temperament names'']</ref>. It is not clear how it later dropped the last letter ''i''.  
This comma was named as ''octagari'' by [[Gene Ward Smith]] in 2005 as a contraction of ''[[octacot]]'' and ''[[garibaldi]]''<ref>[https://yahootuninggroupsultimatebackup.github.io/tuning-math/topicId_12900.html Yahoo! Tuning Group | ''Seven limit comma names from pairs of temperament names'']</ref>. The last letter ''i'' was dropped by 2010, however<ref>[https://yahootuninggroupsultimatebackup.github.io/tuning/topicId_92281.html Yahoo! Tuning Group | ''Octagar (4000/3969) planar temperament'']</ref>.
 
== See also ==
* [[Gallery of just intervals]]


== Notes ==
== References ==


[[Category:Octagar]]
[[Category:Octagar]]
[[Category:Commas named by combining multiple temperament names]]

Latest revision as of 14:18, 13 March 2026

Interval information
Ratio 4000/3969
Factorization 25 × 3-4 × 53 × 7-2
Monzo [5 -4 3 -2
Size in cents 13.46933¢
Name octagar comma
Color name Rurutriyo comma
FJS name [math]\displaystyle{ \text{d}{-2}^{5,5,5}_{7,7} }[/math]
Special properties reduced
Tenney norm (log2 nd) 23.9203
Weil norm (log2 max(n, d)) 23.9316
Wilson norm (sopfr(nd)) 51
Comma size small
S-expression S19⋅S202
Open this interval in xen-calc

The octagar comma is a small 7-limit comma with a ratio of 4000/3969. It is the difference between a stack of three 10/9's and a stack of two 7/6's. It is also the difference between 50/49 and 81/80, and is equal to (10/9)/(21/20)2, with S-expression S19⋅S202, making it a lopsided comma.

Temperaments

Tempering out this comma alone in the 7-limit leads to the octagar temperament. See Octagar family for the family of rank-3 temperaments where it is tempered out. See Octagar temperaments for a collection of rank-2 temperaments where it is tempered out.

Etymology

This comma was named as octagari by Gene Ward Smith in 2005 as a contraction of octacot and garibaldi[1]. The last letter i was dropped by 2010, however[2].

References