From Xenharmonic Wiki
Jump to navigation Jump to search
Interval information
Ratio 250/243
Factorization 2 × 3-5 × 53
Monzo [1 -5 3
Size in cents 49.166137¢
Names porcupine comma,
maximal diesis
Color name y31, triyo 1sn,
Triyo comma
FJS name [math]\text{A1}^{5,5,5}[/math]
Special properties reduced
Tenney height (log2 nd) 15.8906
Weil height (log2 max(n, d)) 15.9316
Wilson height (sopfr (nd)) 32
Harmonic entropy
(Shannon, [math]\sqrt{nd}[/math])
~4.47692 bits
Comma size medium
S-expression S102 × S11
open this interval in xen-calc

250/243 is known as the porcupine comma or the maximal diesis. Measuring about 49 ¢, it is a medium comma. It is the amount by which two minor whole tones exceed a minor third, that is, (10/9)2/(6/5). It is also the difference between 25/24 and 81/80, the two smallest 5-limit superparticular ratios, and an apotome minus three syntonic commas, putting it on the Syntonic-chromatic equivalence continuum.


Tempering it out leads to the 5-limit porcupine temperament. See porcupine family for the family of rank-2 temperaments where it is tempered out.


If we do not temper out this interval and instead use it as an identity of some sort, it serves as the period in the chromium temperament, where it is mapped to 1/24th of the octave. Thus Eliora proposes the name chromium quartertone.