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The 33 equal division divides the octave into 33 equal parts of 36.3636 cents each. It is not especially good at representing all rational intervals in the 7-limit, but it does very well on the 7-limit 3*33 subgroup 2.27.15.21.11.13. On this subgroup it tunes things to the same tuning as 99edo, and as a subgroup patent val it tempers out the same commas. The 99 equal temperaments hemififths, amity, parakleismic, hemiwuerschmidt, ennealimmal and hendecatonic can be reduced to this subgroup and give various possibilities for MOS scales, etc. In particular, the terrain subgroup temperament can be tuned via the 5\33 generator. The full system of harmony provides the optimal patent val for slurpee temperament in the 5, 7, 11 and 13 limits.

While relatively uncommon, 33edo is actually quite an interesting system. As a multiple of 11edo, it approximates the 7th and 11th harmonics via Andrew Heathwaite's 4L+3s Orgone modes (see 26edo). 33edo also tunes the 13th harmonic slightly flat, allowing it to approximate the 21st and 17th harmonics as well, having an 3L+7s of L=4 s=3. It tunes the perfect fifth about 11 cents flat, leading to a near perfect 10/9. The <33 52 76| or 33c val tempers out 81/80 and so leads to a very flat meantone tuning where the major tone is approximately 10/9 in size. Leaving the scale be would result in a flattone 5L+2s of L=5 s=4

Instead of the flat 19\33 fifth you may use the sharp fifth of 20\33, over 25 cents sharp. Two of these lead to a 9/8 of 7\33, which is about 22/19 in size and may be counted as a small third. Between the flat 5\33 version of 9/8 and the sharp 7\33 version there is, of course, a 6\33 = 2\11 11edo interval of 218 cents. Now 6\33 + 5\33 = 11\33 = 1\3 of an octave, or 400 cents, the same major third as 12edo. Also, we have both a 327 minor third from 9\33 = 3\11, the same as the 22edo minor third, and a flatter 8\33 third of 291 cents, which if you like could also be called a flat 19th harmonic, but much more accurately a 13/11 sharp by 1.7 cents (if you use the patent val it is an extremely inaccurate 6/5). Another talent it has is that 7/5 is tuned quite accurately by 16\33, and we may put two 8\33 versions of 13/11 together to produce the cuthbert triad. The 8\33 generator, with MOS of size 5, 9 and 13, gives plenty of scope for these, as well as the 11, 13 and 19 harmonics (taking the generator as a 19/16) which are relatively well in tune.

So while it might not be the most harmonically accurate temperament, it's structurally quite interesting, and it approximates the full 19-limit consort in it's way. You could even say it tunes the 23rd and 29th harmonics ten cents flat if you were so inclined; as well as getting within two cents of the 37th.

pitch: size in cents nearest JI interval(s)
0: 00.000 1/1
1: 36.364 48/47
2: 72.727 24/23
3: 109.091 16/15 17/16
4: 145.455 12/11
5: 181.818 10/9
6: 218.182 8/7 9/8 17/15
7: 254.545 7/6 22/19 37/32
8: 290.909 13/11 19/16
9: 327.273 6/5
10: 363.636 16/13 21/17
11: 400.000 5/4
12: 436.364 9/7
13: 472.727 21/16
14: 509.091 4/3
15: 545.455 11/8
16: 581.818 7/5
17: 618.182 10/7 23/16
18: 654.545 19/13 16/11
19: 690.909 3/2
20: 727.273 32/21
21: 763.636 14/9
22: 800.000 19/12 8/5
23: 836.364 13/8
24: 872.727 5/3
25: 909.091 22/13
26: 945.455 19/11 12/7
27: 981.818 7/4
28: 1018.182 9/5
29: 1054.545 11/6
30: 1090.909 15/8
31: 1127.273 23/12
32: 1163.636 47/24
33: 1200.000 2/1

Nearby Equal Temperaments:
33edo.png

Music:

Deluge Peter Kosmorsky
5 5 1 mode of 33 equal (with video) play by Chris Vaisvil
Bach Contrapunctus 4 Claudi Meneghin version