Satanic comma

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Interval information
Factorization 2-1054 × 3665
Monzo [-1054 665
Size in cents 0.075575483¢
Name satanic comma
FJS name [math]\text{95d}{-64}[/math]
Special properties reduced
Tenney height (log2 nd) 2108
Weil height (log2 max(n, d)) 2108
Wilson height (sopfr (nd)) 4103
Harmonic entropy
(Shannon, [math]\sqrt{nd}[/math])
~1.19987 bits
Comma size unnoticeable
open this interval in xen-calc

The satanic comma (monzo: [-1054 665) is the difference between 666 perfect fifths (octave-reduced) and a single perfect fifth. Equivalently, it is the difference between 665 perfect fifths (octave-reduced) and the unison – but that would not be as devilishly intriguing. This difference is inaudible, at only 0.076 ¢.

It is tempered out in 665edo and its multiples (1330edo, etc.), with 665edo itself being an 11-strong 3-2 telic system due to tempering this comma out.


This comma was named by Marc Jones in 1990[1].