666edo

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666 EDO divides the octave into steps of 1.801 cents each.

Theory

Approximation of prime intervals in 666 EDO
Prime number 2 3 5 7 11 13 17 19 23 29 31 37 41 43
Error absolute (¢) +0.000 +0.748 -0.728 +0.543 +0.033 -0.888 -0.451 -0.216 +0.554 -0.748 -0.891 -0.894 -0.234 +0.194
relative (%) +0 +41 -40 +30 +2 -49 -25 -12 +31 -42 -49 -50 -13 +11
Steps (reduced) 666 (0) 1056 (390) 1546 (214) 1870 (538) 2304 (306) 2464 (466) 2722 (58) 2829 (165) 3013 (349) 3235 (571) 3299 (635) 3469 (139) 3568 (238) 3614 (284)

666edo is appropriate for use with the 2.11.19.41.43 subgroup, a choice with very large prime harmonics. If significant errors are allowed, 666edo can be used with 2.7.11.17.19.23. The alternations between approxmation make 666edo a good choice for "no-number" subgroups which skip particular harmonics.

Using the 666c val, it tempres out 2401/2400, 4375/4374, and 9801/9800 in the 11-limit.

666edo provides good approximations for: 15/11, 16/11, 16/15, 13/12, 13/10, 22/15, 23/14.

666 is divisible by 9, 18, 37, 74, 111, 222, and 333.