EDN
Equal divisions of the natave, which is the mathematical constant e used as a musical interval. e is of particular interest because of its relationship with logarithms, the fact that pitch is perceived logarithmically, and the fact that equal divisions are logarithmic.
Correspondence of EDN to EDO
| Tuning | Equivalent edo | Comment |
|---|---|---|
| 2edn | A stack of two major sixths | |
| 3edn | 2edo | |
| 4edn | Neither are equivalent with 3edo | |
| 5edn | ||
| 6edn | 4edo | With a stretch |
| 7edn | 5edo | |
| 8edn | Entirely misses 2/1, falling halfway between 5edo and 6edo | |
| 9edn | 6edo | With a considerable stretch |
| 10edn | 7edo | |
| 11edn | Neither are equivalent to 8edo | |
| 12edn | ||
| 13edn | 9edo | |
| 14edn | Neither are equivalent to 10edo | |
| 15edn | ||
| 16edn | 11edo | |
| 17edn | 12edo | With a noticeable stretch, given the dominance of 12edo this is more likely to sound like like out of tune 12edo than it's own tuning |
| 18edn | Entirely misses 2/1, falling halfway between 12 and 13edo | |
| 19edn | 13edo | Noticeably compressed |
| 20edn | 14edo | Noticeably stretched |
| 21edn | Entirely misses 2/1, falling halfway between 14edo and 15edo | |
| 22edn | Cannot be considered equivalent to 15edo | |
| 23edn | 16edo | |
| 24edn | 17edo | Some equivalences can be spotted due to 17edo's fame but it's a heavy stretch amounting to 40% |
Zeta function and tuning
In Gene’s black magic formulas, it is mathematically more "natural" to consider the number of divisions to the natave rather than the octave, thus scaling the graph of |Z(x)| horizontally by a factor of 1 instead of 1/ln(2).
The sequence of non-stretched zeta peak edns are 1, 2, 3, 10, 20, 36, 39, 72, 111, 163, 202, 264, 466, 538, 740, 1349, 1887... corresponding to 1, 1, 2, 7, 14, 25, 27, 50, 77, 113, 140, 183, 323, 373, 513, 935, 1308... edos.
Selected divisions
10-EDN
| Step | Cents | Ratio | JI approximation(s) | Interval |
|---|---|---|---|---|
| 0 | 0.0 | 1/1 | 1/1 | unison |
| 1 | 173.12 | e1/10 | 11/10 | flat whole tone |
| 2 | 346.25 | e1/5 | 11/9 | neutral third |
| 3 | 519.37 | e3/10 | 43/32 | sharp fourth |
| 4 | 692.49 | e2/5 | 3/2 | flat fifth |
| 5 | 865.62 | e1/2 | 5/3 | flat major sixth |
| 6 | 1038.74 | e3/5 | 117/64 | neutral seventh |
| 7 | 1211.86 | e7/10 | 2/1 | stretched octave |
| 8 | 1384.99 | e4/5 | 20/9 | flat major ninth |
| 9 | 1558.11 | e9/10 | 22/9 | neutral tenth |
| 10 | 1731.23 | e | 43/16 | natave |
Beyond the natave, some particularly pleasant JI intervals can be found: 11\10 is only 2 cents sharp from 3/1; 13\10 is very close to 11/2; and 23\10 is very close to 10/1. This last approximation in particular makes this equal division almost equivalent to 23-ed(10/1).
10-EDN is similar to 7-EDO in that its step size is roughly 1/7 of an octave, therefore roughly corresponding to the diatonic scale, but with warped, equal-size steps. However, the octave is stretched, which simultaneously helps the extremely flat fifth of 7-EDO.
20-EDN is a doubling of 10-EDN with intervals closer to semitones.
17-EDN
17-EDN is very close to 12-EDO but with slightly sharp semitones (101.84 cents). This causes the octave to be far too sharp (1222.05 cents; essentially double a Pythagorean large tritone) and gives it a rather pleasant sharp fifth of 712.86 cents.
24-EDN
24-EDN has third tones so far sharp of 17-EDO that it becomes a stretched 50-ED8 (50\24 is 3606.74 cents). However, 43\24 is essentially the 6th harmonic (1514.83+1586.965=3101.79 cents)..