109edo is the equal division of the octave into 109 parts of 11.009 cents each. It tempers out 20000/19683 in the 5-limit; 245/243, 2401/2400 and 65625/65536 in the 7-limit; 385/384, 1375/1372, and 4000/3993 in the 11-limit. It provides the optimal patent val for 7-limit octacot temperament, and 11 and 13 limit leapweek; plus 109ef provides an excellent tuning for 11- and 13-limit octacot.

109edo is the 29th prime EDO.


Since 109edo has a step of 11.009 cents, it also allows one to use its MOS scales as circulating temperaments. It is also the first edo which also allows one to use an MOS scale one octave of which fills a standard piano keyboard as a circulating temperament.

Circulating temperaments in 109edo
Tones Pattern L:s
5 4L 1s 22:21
6 1L 5s 19:18
7 4L 3s 16:15
8 5L 3s 14:13
9 1L 8s 13:12
10 9L 1s 11:10
11 10L 1s 10:9
12 1L 11s
13 4L 9s 9:8
14 11L 3s 8:7
15 4L 11s
16 13L 3s 7:6
17 7L 10s
18 1L 17s
19 14L 5s 6:5
20 9L 11s
21 4L 17s
22 21L 1s 5:4
23 17L 6s
24 13L 11s
25 9L 16s
26 5L 21s
27 1L 26s
28 25L 3s 4:3
29 22L 7s
30 19L 11s
31 16L 15s
32 13L 19s
33 10L 23s
34 7L 27s
35 4L 31s
36 1L 35s
37 35L 2s 3:2
38 33L 5s
39 31L 8s
40 29L 11s
41 27L 14s
42 25L 17s
43 23L 20s
44 21L 23s
45 19L 26s
46 17L 29s
47 15L 32s
48 13L 35s
49 11L 38L
50 9L 41s
51 7L 44s
52 5L 47s
53 3L 50s
54 1L 53s
55 54L 1s 2:1
56 53L 3s
57 52L 5s
58 51L 7s
59 50L 9s
60 49L 11s
61 48L 13s
62 47L 15s
63 46L 17s
64 45L 19s
65 44L 21s
66 43L 23s
67 42L 25s
68 41L 27s
69 40L 29s
70 39L 31s
71 38L 33s
72 37L 35s
73 36L 37s
74 35L 39s
75 34L 41s
76 33L 43s
77 32L 45s
78 31L 47s
79 30L 49s
80 29L 51s
81 28L 53s
82 27L 55s
83 26L 57s
84 25L 59s
85 24L 61s
86 23L 63s
87 22L 65s