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{{Infobox Interval
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| Name = rastma, neutral third comma
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'''243/242''', the '''rastma''' or the '''neutral third comma''', is a [[small comma|small]] [[11-limit]] (also [[2.3.11 subgroup|2.3.11-subgroup]]) [[comma]] with a value of roughly 7.1 [[cent]]s. It is significant in [[just intonation]] as the amount by which a stack of two [[11/9]] neutral thirds (that is an Alpharabian narrow fifth
'''243/242''', the '''rastma''' or the '''neutral third comma''', is an [[11-limit]] (also 2.3.11 subgroup) comma with a value of roughly 7.1 [[cent]]s. It is significant in Just Intonation as the amount by which a stack of two [[11/9]] neutral thirds fall short of [[3/2]] just perfect fifth, by which a stack of two [[33/32]] quartertones falls short of an [[2187/2048|apotome (2187/2048)]] as well as the difference between [[11/9]] and [[27/22]], and, the difference between [[45/44]] and [[55/54]]. The last makes the theory where the rastma serves as the [[Diatonic, Chromatic, Enharmonic, Subchromatic|subchroma]] that separates greater and lesser 11-limit chromas – a theory that becomes especially useful when one works extensively with high-fidelity renditions of the 11-limit.  
[[121/81]]) fall short of [[3/2]] just perfect fifth as well as the amount by which a stack of two [[27/22]] neutral thirds (that is an Alpharabian wide fifth [[729/484]]) exceeds a 3/2 just perfect fifth, the amount by which a stack of two [[33/32]] quartertones falls short of an [[2187/2048|apotome (2187/2048)]] as well as the difference between 11/9 and 27/22, and the difference between [[45/44]] and [[55/54]]. The last makes the theory where the rastma serves as the [[subchromatic|subchroma]] that separates greater and lesser 11-limit chromas – a theory that becomes especially useful when one works extensively with high-fidelity renditions of the 11-limit.


== Temperaments ==
== Temperaments ==
Tempering it out in the full 11-limit leads to the rastmic temperament, enabling [[rastmic chords]], or, in the 2.3.11 subgroup, the [[Subgroup temperaments #Neutral|neutral]] temperament, enabling [[Neutral tetrad|neutral chords]].
[[Tempering out]] this comma in the full 11-limit leads to the [[rastmic]] rank-4 temperament, or in the 2.3.11 subgroup, the [[neutral (temperament)|neutral]] temperament, enabling [[rastmic chords]] in either case.  
 
=== Rastmic ===
Subgroup: 2.3.5.7.11
 
[[Comma list]]: 243/242
 
[[Mapping]]: [{{val| 1 1 0 0 2 }}, {{val| 0 2 0 0 5 }}, {{val| 0 0 1 0 0 }}, {{val| 0 0 0 1 0}}]
 
[[POTE tuning]]: ~11/9 = 350.5254, ~5/4 = 386.1653, ~7/4 = 968.6464
 
{{Val list|legend=1| 7d, 10, 14c, 17c, 24, 27e, 31, 41, 58, 72, 130, 202 }}
 
[[Badness]]: 0.05088 × 10<sup>-6</sup>
 
=== Neutral ===
Subgroup: 2.3.11
 
[[Comma list]]: 243/242
 
[[Sval]] [[mapping]]: [{{val| 1 1 2 }}, {{val| 0 2 5 }}]
 
[[Gencom]] [[mapping]]: [{{val| 1 1 0 0 2 }}, {{val| 0 2 0 0 5 }}]
 
Gencom: [2 11/9; 243/242]
 
[[POTE tuning]]: ~11/9 = 350.525
 
{{Val list|legend=1| 7, 10, 17, 24, 65, 89, 202, 291, 380 }}


[[Tp tuning #T2 tuning|RMS error]]: 0.3021 cents
See [[Rastmic clan]] for the clan of rank-2 temperaments where it is tempered out. See [[Rastmic rank three clan|Rastmic rank-3 clan]] for the clan of rank-3 temperaments where it is tempered out.


== See also ==
== See also ==
* [[Rank-4 temperament #Rastmic (243/242)]]
* [[Rastmic rank three clan]], the clan of rank-3 temperaments where it is tempered out
* [[Rastmic chords]]
* [[Small comma]]
* [[List of superparticular intervals]]
* [[List of superparticular intervals]]


[[Category:Rastmic]]
[[Category:Rastmic]]
[[Category:Neutral]]
[[Category:Neutral]]
[[Category:Commas named after musical traditions]]
[[Category:Commas named for the generator of their temperament]]