217edo
217EDO is the equal division of the octave into 217 parts of 5.529954 cents each. It is a strong 19-limit system, the smallest uniquely consistent in the 19-limit and consistent to the 21-limit. It shares the same 5th and 7th harmonics with 31EDO (217 = 7 × 31), as well as the 11/9 interval (supporting the birds temperament). However, compared to 31EDO, its patent vals differ on the mappings for 3, 11, 13, 17 and 19 – in fact, this EDO has a very accurate 13th harmonic, as well as the 19/15 interval. It tempers out the parakleisma, [8 14 -13⟩, and the escapade comma, [32 -7 -9⟩ in the 5-limit; 3136/3125, 4375/4374, 10976/10935 and 823543/819200 in the 7-limit; 441/440, 4000/3993 and 5632/5625 in the 11-limit; 364/363, 676/675, 1001/1000, 1575/1573 and 2080/2079 in the 13-limit; 595/594, 833/832, 936/935, 1156/1155, 1225/1224, 1701/1700 in the 17-limit; 343/342, 476/475, 969/968, 1216/1215, 1445/1444, 1521/1520 and 1540/1539 in the 19-limit. It provides the optimal patent val for the 11- and 13-limit arch and the 11- and 13-limit cotoneum.
Just approximation
| Prime number | 2 | 3 | 5 | 7 | 11 | 13 | 17 | 19 | 23 | 29 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Error | absolute (¢) | 0.0 | +0.349 | +0.783 | -1.084 | +1.677 | +0.025 | +0.114 | +1.104 | +2.140 | -1.006 | -0.335 |
| relative (%) | 0.0 | +6.31 | +14.16 | -19.60 | +30.33 | +0.46 | +2.06 | +19.97 | +38.71 | -18.19 | -6.06 | |
| Degree (reduced) | 217 (0) | 344 (127) | 504 (70) | 609 (175) | 751 (100) | 803 (152) | 887 (19) | 922 (54) | 982 (114) | 1054 (186) | 1075 (207) | |
Selected just intervals
The following table shows how 23-odd-limit intervals are represented in 217EDO. Prime harmonics are in bold; inconsistent intervals are in italic.
| Interval, complement | Error (abs, ¢) |
|---|---|
| 16/13, 13/8 | 0.025 |
| 19/15, 30/19 | 0.028 |
| 10/9, 9/5 | 0.085 |
| 17/13, 26/17 | 0.088 |
| 17/16, 32/17 | 0.114 |
| 24/17, 17/12 | 0.235 |
| 20/19, 19/10 | 0.321 |
| 13/12, 24/13 | 0.324 |
| 4/3, 3/2 | 0.349 |
| 19/18, 36/19 | 0.406 |
| 6/5, 5/3 | 0.434 |
| 23/22, 44/23 | 0.463 |
| 15/11, 22/15 | 0.545 |
| 22/19, 19/11 | 0.573 |
| 18/17, 17/9 | 0.585 |
| 20/17, 17/10 | 0.669 |
| 18/13, 13/9 | 0.673 |
| 9/8, 16/9 | 0.698 |
| 21/16, 32/21 | 0.735 |
| 24/19, 19/12 | 0.755 |
| 26/21, 21/13 | 0.760 |
| 13/10, 20/13 | 0.758 |
| 5/4, 8/5 | 0.783 |
| 21/17, 34/21 | 0.849 |
| 11/10, 20/11 | 0.894 |
| 11/9, 18/11 | 0.979 |
| 19/17, 34/19 | 0.991 |
| 30/23, 23/15 | 1.008 |
| 17/15, 30/17 | 1.018 |
| 23/19, 38/23 | 1.036 |
| 26/19, 19/13 | 1.079 |
| 8/7, 7/4 | 1.084 |
| 19/16, 32/19 | 1.104 |
| 15/13, 26/15 | 1.107 |
| 14/13, 13/7 | 1.109 |
| 16/15, 15/8 | 1.132 |
| 17/14, 28/17 | 1.198 |
| 12/11, 11/6 | 1.328 |
| 23/20, 40/23 | 1.357 |
| 7/6, 12/7 | 1.433 |
| 23/18, 36/23 | 1.442 |
| 21/20, 40/21 | 1.518 |
| 22/17, 17/11 | 1.564 |
| 13/11, 22/13 | 1.652 |
| 11/8, 16/11 | 1.677 |
| 9/7, 14/9 | 1.782 |
| 24/23, 23/12 | 1.791 |
| 21/19, 38/21 | 1.839 |
| 7/5, 10/7 | 1.867 |
| 23/17, 34/23 | 2.027 |
| 26/23, 23/13 | 2.115 |
| 32/23, 23/16 | 2.140 |
| 19/14, 28/19 | 2.188 |
| 15/14, 28/15 | 2.216 |
| 28/23, 23/14 | 2.306 |
| 22/21, 21/11 | 2.412 |
| 23/21, 42/23 | 2.655 |
| 14/11, 11/7 | 2.761 |