Tetracot comma: Difference between revisions

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20000/19683, the tetracot [[Comma|comma]] or minimal diesis, is an interval of 27.660 cents which is the amount by which four [[10/9|minor whole tones]] exceed a fifth; that is, (10/9)^4/(3/2). Tempering it out leads to [[Tetracot_family|tetracot temperament]].
{{Infobox Interval
[[Category:comma]]
| Ratio = 20000/19683
[[Category:tetracot]]
| Name = tetracot comma, minimal diesis
| Color name = sy<sup>4</sup>1, Saquadyo comma
| Comma = yes
}}
The '''tetracot comma''' ({{monzo|legend=1| 5 -9 4 }}, [[ratio]]: 20000/19683), or '''minimal diesis''', is a [[small comma|small]] [[5-limit]] [[comma]] of 27.660 [[cent]]s which is the amount by which four [[10/9|minor whole tones]] exceed a [[3/2|fifth]]; that is, (10/9)<sup>4</sup>/(3/2). It can also be expressed as the octave-reduced difference between four [[5/4|just major thirds]] and nine just perfect fifths, which directly follows from its monzo. Another characterization is the interval between four [[81/80|syntonic commas]] and a [[2187/2048|Pythagorean apotome]], making the corresponding temperament a member of the [[syntonic&ndash;chromatic equivalence continuum]]. Since an apotome minus two syntonic commas is a [[25/24|classical chroma]], the comma can be expressed as the difference between an apotome and a stack of two classical chromas, or between a classical chroma and a stack of two syntonic commas.
 
== Temperaments ==
Tempering out this comma leads to the [[tetracot family]] of temperaments.
 
[[Category:Tetracot]]
[[Category:Commas named for how they divide the fifth]]