Würschmidt comma

Interval information

Ratio	393216/390625
Factorization	217 × 3 × 5-8
Monzo	[17 1 -8⟩
Size in cents	11.44529¢
Name	Würschmidt comma
Color name	sg83, Saquadbigu comma
FJS name	[math]\displaystyle{ \text{dddd3}_{5,5,5,5,5,5,5,5} }[/math]
Special properties	reduced
Tenney norm (log2 nd)	37.1604
Weil norm (log2 max(n, d))	37.1699
Wilson norm (sopfr(nd))	77
Comma size	small
Open this interval in xen-calc

The Würschmidt comma ([17 1 -8⟩ = 393216/390625) is a small 5-limit comma of 11.4 cents.

It is the amount by which an octave-reduced stack of eight classical major thirds falls short of a perfect fifth: (5/4)⁸(393216/390625)/4 = 3/2, which comes from 5/4 being a convergent in the continued fraction of [math]\displaystyle{ \sqrt[8]{6} }[/math]. It is also equal to the difference between seven major thirds and 24/5 (i.e. 6/5 plus two octaves). In other words, (5/4)⁷(393216/390625)/4 = 6/5.

In terms of commas it is the difference between the lesser diesis and the magic comma, (128/125)/(3125/3072).

Tempering it out leads to the würschmidt family of temperaments. As in meantone, it implies that 3/2 will be tempered flat and/or 5/4 will be tempered sharp, and therefore 6/5 will be tempered flat.