Betarabian comma: Difference between revisions

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The '''Betarabian comma''' ({{monzo|legend=1| -18 7 0 0 2 }}, [[ratio]]: 264627/262144) is a [[small comma|small]] [[11-limit]] [[comma]] measuring about 16.3{{cent}}. It forms the difference between various pairs of enharmonic [[quartertone]]-based intervals in the [[2.3.11 subgroup]]. Specifically, it is the amount by which a stack of two [[33/32]]'s exceeds the [[Pythagorean limma]], or the amount by which a stack of two [[11/8]]'s exceeds the [[4096/2187|Pythagorean diminished octave]].  
The '''Betarabian comma''' ({{monzo|legend=1| -18 7 0 0 2 }}, [[ratio]]: 264627/262144) is a [[small comma|small]] [[11-limit]] [[comma]] measuring about 16.3{{cent}}. It forms the difference between various pairs of enharmonic [[quartertone]]-based intervals in the [[2.3.11 subgroup]]. Specifically, it is the amount by which a stack of two [[33/32]]'s exceeds the [[Pythagorean limma]], or the amount by which a stack of two [[11/8]]'s exceeds the [[4096/2187|Pythagorean diminished octave]].  


It is the sum of the [[Alpharabian comma]] and the [[243/242|rastma]], as well as the sum of the [[32805/32768|schisma]] and the [[121/120|biyatisma]] in the [[2.3.5.11 subgroup]].  
It factors into simpler commas as the sum of the [[Alpharabian comma]] and the [[243/242|rastma]]. In the [[2.3.5.11 subgroup]], it also factors as the sum of the [[32805/32768|schisma]] and the [[121/120|biyatisma]].  


== Temperaments ==
== Temperaments ==
As the Betarabian comma is the sum of the Alpharabian comma and the rastma, it is automatically tempered out whenever the rastma and the Alpharabian comma are tempered out; however, there are other temperaments that temper out just the Betarabian comma itself. When tempered out in the 11-limit, it is the '''betaxenic''' temperament, or in the [[2.3.11 subgroup]], the '''betaxenean''' temperament.  
As the Betarabian comma is the sum of the Alpharabian comma and the rastma, it is automatically tempered out whenever the rastma and the Alpharabian comma are tempered out; however, there are other temperaments that temper out just the Betarabian comma itself. When tempered out in the 11-limit, it is the '''betaxenic''' temperament, or in the [[2.3.11 subgroup]], the [[betaxenean]] temperament.  


== Etymology ==
== Etymology ==