3136/3125
Interval information |
didacus comma
3136/3125, the hemimean comma or didacus comma, is a 7-limit small comma measuring about 6.1 ¢. It is the difference between five classic major thirds (5/4) and two subminor sevenths (7/4); it is also the difference between the septimal semicomma (126/125) and the septimal kleisma (225/224).
Temperaments
Didacus (2.5.7)
Tempering out this comma in its minimal prime subgroup of 2.5.7 leads to didacus (a variant of hemithirds without a mapping for 3) with a generator of 28/25.
Hemimean (2.3.5.7)
Tempering out this comma in the full 7-limit leads to the rank-3 hemimean family of temperaments, which splits the syntonic comma into two equal parts, each representing 126/125~225/224. (Note that if we temper both of those commas individually we get septimal meantone.)
Orion (2.5.7.17.19)
As 28/25 is close to 19/17 and as the latter is a precise approximation of half of 5/4, it is natural to temper (28/25)/(19/17) = 476/475 and the semiparticular (5/4)/(19/17)2 = 1445/1444 which together imply tempering 3136/3125 and 2128/2125, resulting in a rank 3 temperament.
Mapping:
[⟨1 0 -3 0 -1]
⟨0 2 5 0 1]
⟨0 0 0 1 1]]
CTE generators: 2/1, ~28/25 = 193.642, ~17/16 = 104.434
See also
- Hemimean family, the rank-3 family where it is tempered out
- Hemimean clan, the rank-2 clan where it is tempered out