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Interval information
Ratio 243/242
Monzo [-1 5 0 0 -2
Size in cents 7.13912
Name(s) rastma,
neutral third comma
FJS name A1121

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 cents. It is significant in Just Intonation as the amount by which a stack of two 33/32 quartertones falls short of an apotome (2187/2048) as well as the difference between 11/9 and 27/22, and, the difference between 45/44 and 55/54. Tempering it out leads to a form of rastmic temperament or neutral temperament. When not tempered out, the rastma serves as the subchroma that separates greater and lesser 11-limit chromas– a property that becomes especially apparent when one works extensively with the 11-limit.

See also