21/13: Difference between revisions

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{{Infobox Interval
{{Infobox Interval
| Ratio = 21/13
| Monzo = 0 1 0 1 0 -1
| Cents = 830.25325
| Name = tridecimal supraminor sixth
| Name = tridecimal supraminor sixth
| Color name = thuzo 6th, 3uz6
| Color name = thuzo 6th, 3uz6
| FJS name = M6<sup>7</sup><sub>13</sub>
| Sound = ji-21-13-csound-foscil-220hz.mp3
| Sound = ji-21-13-csound-foscil-220hz.mp3
}}
}}


'''21/13''', the '''tridecimal supraminor sixth''', is ''ca''. 830 [[cent]]s in size. It has a very good approximation in [[13edo]].
'''21/13''', the '''tridecimal supraminor sixth''', is ''ca''. 830 [[cent]]s in size. It has a very good approximation in [[13edo]], and notably, 5 of these intervals differ from [[11/1]] by 4084223/4084101, a comma of a mere 0.052{{cent}}.


This interval is a ratio of two consecutive Fibonacci numbers, therefore it approximates the [[golden ratio]]. In this case, 21/13 is ~2.8 [[cent|¢]] flat of the golden ratio.
This interval is a ratio of two consecutive {{w|Fibonacci numbers}} and thus a convergent to [[acoustic phi]] (the interval of a [[golden ratio]]). In this case, 21/13 is ~2.8{{cent}} flat of acoustic phi. It differs from [[13/8]], the previous such convergent, by [[169/168]], and from the following convergent [[34/21]] by [[442/441]].


== See also ==
== See also ==
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* [[Gallery of just intervals]]
* [[Gallery of just intervals]]


[[Category:13-limit]]
[[Category:Sixth]]
[[Category:Sixth]]
[[Category:Supraminor sixth]]
[[Category:Supraminor sixth]]
[[Category:Golden ratio approximations]]
[[Category:Golden ratio approximations]]

Latest revision as of 05:32, 8 August 2025

Interval information
Ratio 21/13
Factorization 3 × 7 × 13-1
Monzo [0 1 0 1 0 -1
Size in cents 830.2532¢
Name tridecimal supraminor sixth
Color name thuzo 6th, 3uz6
FJS name [math]\displaystyle{ \text{M6}^{7}_{13} }[/math]
Special properties reduced
Tenney height (log2 nd) 8.09276
Weil height (log2 max(n, d)) 8.78463
Wilson height (sopfr(nd)) 23

[sound info]
Open this interval in xen-calc

21/13, the tridecimal supraminor sixth, is ca. 830 cents in size. It has a very good approximation in 13edo, and notably, 5 of these intervals differ from 11/1 by 4084223/4084101, a comma of a mere 0.052 ¢.

This interval is a ratio of two consecutive Fibonacci numbers and thus a convergent to acoustic phi (the interval of a golden ratio). In this case, 21/13 is ~2.8 ¢ flat of acoustic phi. It differs from 13/8, the previous such convergent, by 169/168, and from the following convergent 34/21 by 442/441.

See also