4375/4374
Interval information |
Zoquadyo comma
reduced
(Shannon, [math]\displaystyle{ \sqrt{nd} }[/math])
4375/4374, the ragisma, is an unnoticeable 7-limit comma which is the difference between a stack of two large limmas and 7/6, the difference between a stack of four classical whole tones (10/9) and 32/21, and the difference between a stack of four classical minor thirds (6/5) octave-reduced and 28/27. It is the smallest 7-limit superparticular ratio. It is also equal to the difference between a kleisma (S252 × S26) and a marvel comma (S15 = S25 × S26 × S27), hence its expression as S25 / S27 which directly implies it can be expressed as (28/24 = 7/6)/(27/25)2.
Temperaments
Tempering out this comma leads to the ragismic temperament, enabling ragismic chords in the 27-odd-limit. See Ragismic family for the rank-3 family where it is tempered out. See Ragismic microtemperaments for a collection of rank-2 temperaments where it is tempered out.
Etymology
This comma was allegedly named by Erv Wilson no later than 2001[1]. Interestingly, by 2004 people had already lost track of its origin and meaning[2]. It is speculated that it could have been named after Indian ragas.