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Interesting phenomena may be observed when adding the cardinality of one equal division to that of another (octave or not). This really amounts to the consideration of adding the associated [[vals]], which are the mappings to primes larger than 2. An EDO is defined by a certain number of steps equating to 2; if we have more steps equating to 3, we get a 3-limit val, and so forth. So, for example, 12edo can be written {{val| 12 }}, saying that twelve steps maps to 2, but the 3-limit val for 12 is {{val| 12 19 }}, telling us that 19 steps maps to 3, and the 5-limit val is {{val| 12 19 28 }}, telling us that 28 steps maps to 5. | Interesting phenomena may be observed when adding the cardinality of one equal division to that of another (octave or not). This really amounts to the consideration of adding the associated [[vals]], which are the mappings to primes larger than 2. An EDO is defined by a certain number of steps equating to 2; if we have more steps equating to 3, we get a 3-limit val, and so forth. So, for example, 12edo can be written {{val| 12 }}, saying that twelve steps maps to 2, but the 3-limit val for 12 is {{val| 12 19 }}, telling us that 19 steps maps to 3, and the 5-limit val is {{val| 12 19 28 }}, telling us that 28 steps maps to 5. | ||
If we add 12 and 19 we get another good division, 12 + 19 = 31. We can understand why this works if we look at it as adding vals; {{val| 12 19 28 }} + {{val| 19 30 44 }} = {{val| 31 49 72 }}. The relative error in terms of [[relative cent]]s is additive, and so sharpness and flatness cancel out, as they do for example with the approximation to 5 when adding 12 and 19. In terms of relative cents, the error of 12edo for the primes 3 and 5 is [ | If we add 12 and 19 we get another good division, {{nowrap|12 + 19 {{=}} 31}}. We can understand why this works if we look at it as adding vals; {{nowrap|{{val| 12 19 28 }} + {{val| 19 30 44 }} {{=}} {{val| 31 49 72 }}}}. The relative error in terms of [[relative cent]]s is additive, and so sharpness and flatness cancel out, as they do for example with the approximation to 5 when adding 12 and 19. In terms of relative cents, the error of 12edo for the primes 3 and 5 is [−1.955 13.686] (the same as absolute cents) and the error of 19edo is [−11.429 −11.663], and this sums to [−13.384 2.023]. In relative cents the error of the fifth for 31edo is not much increased from 19edo, and on converting to absolute cents we find it is even better, and the error of the major third is much smaller due to the cancellation. When the errors are very sharp in one direction and very flat in another, as for instance with 15edo and 16edo, the sum (again 31edo) can have a much smaller error due to the cancellation. 24edo's flat fifth and 29edo's sharp fifth can be added to form 53edo. | ||
We may also look at addition of EDOs in terms of MOS; if ''a''\''n'' is a generator for an ''n''-edo MOS, and ''b''\''m'' for an ''m''-edo MOS, where both of these are generators for the same linear temperament, then the mediant, (''a'' + ''b'')\(''n'' + ''m''), will be a generator for a MOS for the same temperament, this time in (''n'' + ''m'')-edo. A visual way of putting this is that through this addition of ''n'' and ''m'', one becomes the accidentals or black keys, and the other the naturals or white keys. The choice of accidental/natural or black keys/white keys is a question of emphasis on the part of the composer or designer. Furthermore, one may add more than two numbers, hierarchically expanding the possibilities to double flats and sharps and beyond. This can be useful in designing keyboards and systems of notation. | We may also look at addition of EDOs in terms of MOS; if ''a''\''n'' is a generator for an ''n''-edo MOS, and ''b''\''m'' for an ''m''-edo MOS, where both of these are generators for the same linear temperament, then the mediant, {{nowrap|(''a'' + ''b'')\(''n'' + ''m'')}}, will be a generator for a MOS for the same temperament, this time in {{nowrap|(''n'' + ''m'')}}-edo. A visual way of putting this is that through this addition of ''n'' and ''m'', one becomes the accidentals or black keys, and the other the naturals or white keys. The choice of accidental/natural or black keys/white keys is a question of emphasis on the part of the composer or designer. Furthermore, one may add more than two numbers, hierarchically expanding the possibilities to double flats and sharps and beyond. This can be useful in designing keyboards and systems of notation. | ||
=== Size of an EDO === | === Size of an EDO === | ||
When an edo divides the octave into fewer than 12 divisions (so that each step exceeds 100 cents), you might call it a [[macrotonal EDO]]. Of these, 1, 2, 3, 4, and 6 divide 12 and so are already available to anyone wishing to explore them. {{EDOs|5, 7, and 9}} have arguably been used in various kinds of musical traditions in different parts of the world. [https://soundcloud.com/scottthompson-3/the-13-edos-of-xmas ''The 13 EDOs of Xmas''] by [[Scott Thompson]] is a humorous demonstration of EDOs 1–13. | |||
When an edo divides the octave into fewer than 12 divisions (so that each step exceeds 100 cents), you might call it a [[macrotonal EDO]]. Of these, 1, 2, 3, 4 and 6 divide 12 and so are already available to anyone wishing to explore them. | |||
On the other hand, if you use the edo to tune a scale or [[regular temperament]], the size of the edo does not matter so much (at least conceptually), as you don't need to use all of it. Some of the EDOs which can be used to tune various temperaments are listed on the [[optimal patent val]] page. Tuning a scale in just intonation by one of these EDOs can be regarded as automatically tempering it to the corresponding regular temperament. | On the other hand, if you use the edo to tune a scale or [[regular temperament]], the size of the edo does not matter so much (at least conceptually), as you don't need to use all of it. Some of the EDOs which can be used to tune various temperaments are listed on the [[optimal patent val]] page. Tuning a scale in just intonation by one of these EDOs can be regarded as automatically tempering it to the corresponding regular temperament. | ||
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=== What's the difference between EDOs and Equal Temperaments? === | === What's the difference between EDOs and Equal Temperaments? === | ||
: {{Main|EDO vs ET}} | |||
== Individual pages for EDOs == | == Individual pages for EDOs == | ||
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{{See also| Pergen #Pergens and EDOs }} | {{See also| Pergen #Pergens and EDOs }} | ||
[[Pergen]]s provide a JI-agnostic way to name the rank-2 scales of an EDO. This table lists every possible period/generator combination for EDOs 5-24, and for each coprime combination, the simplest pergen that it can represent. Non-coprime combinations such as P = 6\12, G = 4\12 are marked as " | [[Pergen]]s provide a JI-agnostic way to name the rank-2 scales of an EDO. This table lists every possible period/generator combination for EDOs 5-24, and for each coprime combination, the simplest pergen that it can represent. Non-coprime combinations such as {{nowrap|P {{=}} 6\12}}, {{nowrap|G {{=}} 4\12}} are marked as "—". | ||
{| class="wikitable" | {| class="wikitable" | ||
| Line 414: | Line 413: | ||
! 6 = P8 | ! 6 = P8 | ||
| P4/2 | | P4/2 | ||
| | | — | ||
| | | | ||
| | | | ||
| Line 455: | Line 454: | ||
! 8 = P8 | ! 8 = P8 | ||
| P4/3 | | P4/3 | ||
| | | — | ||
| P5 | | P5 | ||
| | | | ||
| Line 468: | Line 467: | ||
! 4 = P8/2 | ! 4 = P8/2 | ||
| P5 | | P5 | ||
| | | — | ||
| | | | ||
| | | | ||
| Line 483: | Line 482: | ||
| P4/4 | | P4/4 | ||
| P4/2 | | P4/2 | ||
| | | — | ||
| P5 | | P5 | ||
| | | | ||
| Line 509: | Line 508: | ||
! 10 = P8 | ! 10 = P8 | ||
| P4/4 | | P4/4 | ||
| | | — | ||
| P5/2 | | P5/2 | ||
| | | — | ||
| | | | ||
| | | | ||
| Line 550: | Line 549: | ||
! 12 = P8 | ! 12 = P8 | ||
| P4/5 | | P4/5 | ||
| | | — | ||
| | | — | ||
| | | — | ||
| P5 | | P5 | ||
| | | | ||
| Line 563: | Line 562: | ||
! 6 = P8/2 | ! 6 = P8/2 | ||
| P5 | | P5 | ||
| | | — | ||
| | | — | ||
| | | | ||
| | | | ||
| Line 576: | Line 575: | ||
! 4 = P8/3 | ! 4 = P8/3 | ||
| P5 | | P5 | ||
| | | — | ||
| | | | ||
| | | | ||
| Line 617: | Line 616: | ||
! 14 = P8 | ! 14 = P8 | ||
| P4/6 | | P4/6 | ||
| | | — | ||
| P4/2 | | P4/2 | ||
| | | — | ||
| P11/4 | | P11/4 | ||
| | | — | ||
| | | | ||
| | | | ||
| Line 645: | Line 644: | ||
| P4/6 | | P4/6 | ||
| P4/3 | | P4/3 | ||
| | | — | ||
| P12/6 | | P12/6 | ||
| | | — | ||
| | | — | ||
| P11/3 | | P11/3 | ||
| | | | ||
| Line 684: | Line 683: | ||
! 16 = P8 | ! 16 = P8 | ||
| P4/7 | | P4/7 | ||
| | | — | ||
| P5/3 | | P5/3 | ||
| | | — | ||
| P12/5 | | P12/5 | ||
| | | — | ||
| P5 | | P5 | ||
| | | | ||
| Line 697: | Line 696: | ||
! 8 = P8/2 | ! 8 = P8/2 | ||
| P5 | | P5 | ||
| | | — | ||
| P5/3 | | P5/3 | ||
| | | — | ||
| | | | ||
| | | | ||
| Line 710: | Line 709: | ||
! 4 = P8/4 | ! 4 = P8/4 | ||
| P5 | | P5 | ||
| | | — | ||
| | | | ||
| | | | ||
| Line 738: | Line 737: | ||
! 18 = P8 | ! 18 = P8 | ||
| P4/8 | | P4/8 | ||
| | | — | ||
| | | — | ||
| | | — | ||
| P5/2 | | P5/2 | ||
| | | — | ||
| P12/4 | | P12/4 | ||
| | | — | ||
| | | | ||
| | | | ||
| Line 752: | Line 751: | ||
| P5 | | P5 | ||
| P4/4 | | P4/4 | ||
| | | — | ||
| P4/2 | | P4/2 | ||
| | | | ||
| Line 764: | Line 763: | ||
! 6 = P8/3 | ! 6 = P8/3 | ||
| P5/2 | | P5/2 | ||
| | | — | ||
| | | — | ||
| | | | ||
| | | | ||
| Line 805: | Line 804: | ||
! 20 = P8 | ! 20 = P8 | ||
| P4/8 | | P4/8 | ||
| | | — | ||
| P5/4 | | P5/4 | ||
| | | — | ||
| | | — | ||
| | | — | ||
| P11/4 | | P11/4 | ||
| | | — | ||
| c<sup>3</sup>P5/8 | | c<sup>3</sup>P5/8 | ||
| | | | ||
| Line 818: | Line 817: | ||
! 10 = P8/2 | ! 10 = P8/2 | ||
| M2/4 | | M2/4 | ||
| | | — | ||
| P5/4 | | P5/4 | ||
| | | — | ||
| | | — | ||
| | | | ||
| | | | ||
| Line 844: | Line 843: | ||
! 4 = P8/5 | ! 4 = P8/5 | ||
| P5/4 | | P5/4 | ||
| | | — | ||
| | | | ||
| | | | ||
| Line 859: | Line 858: | ||
| P4/9 | | P4/9 | ||
| P5/6 | | P5/6 | ||
| | | — | ||
| P5/3 | | P5/3 | ||
| P11/6 | | P11/6 | ||
| | | — | ||
| | | — | ||
| c<sup>3</sup>P4/9 | | c<sup>3</sup>P4/9 | ||
| | | — | ||
| P11/3 | | P11/3 | ||
| | | | ||
| Line 898: | Line 897: | ||
! 22 = P8 | ! 22 = P8 | ||
| P4/9 | | P4/9 | ||
| | | — | ||
| P4/3 | | P4/3 | ||
| | | — | ||
| P12/7 | | P12/7 | ||
| | | — | ||
| P12/5 | | P12/5 | ||
| | | — | ||
| P5 | | P5 | ||
| | | — | ||
| | | | ||
|- | |- | ||
| Line 939: | Line 938: | ||
! 24 = P8 | ! 24 = P8 | ||
| P4/10 | | P4/10 | ||
| | | — | ||
| | | — | ||
| | | — | ||
| P4/2 | | P4/2 | ||
| | | — | ||
| P5/2 | | P5/2 | ||
| | | — | ||
| | | — | ||
| | | — | ||
| c<sup>4</sup>P5/10 | | c<sup>4</sup>P5/10 | ||
|- | |- | ||
! 12 = P8/2 | ! 12 = P8/2 | ||
| M2/4 | | M2/4 | ||
| | | — | ||
| | | — | ||
| | | — | ||
| P4/2 | | P4/2 | ||
| | | | ||
| Line 965: | Line 964: | ||
! 8 = P8/3 | ! 8 = P8/3 | ||
| P5/2 | | P5/2 | ||
| | | — | ||
| P4/2 | | P4/2 | ||
| | | | ||
| Line 978: | Line 977: | ||
! 6 = P8/4 | ! 6 = P8/4 | ||
| P4/2 | | P4/2 | ||
| | | — | ||
| | | — | ||
| | | | ||
| | | | ||
| Line 991: | Line 990: | ||
! 4 = P8/6 | ! 4 = P8/6 | ||
| P4/2 | | P4/2 | ||
| | | — | ||
| | | | ||
| | | | ||