12edo
Prime factorization | 2^{2} × 3 |
Step size | 100¢^{by definition} |
Fifth | 7\12 (700¢) |
Major 2nd | 2\12 (200¢) |
Semitones (A1:m2) | 1:1 (100¢:100¢) |
Consistency limit | 9 |
Monotonicity limit | 11 |
12 equal divisions of the octave (12edo), or 12(-tone) equal temperament (12-TET, 12ET) when viewed from a regular temperament perspective, is the predominating tuning system in the world today.
Theory
Harmonic | 2 | 3 | 5 | 7 | 11 | 13 | 17 | 19 | 23 | 29 | |
---|---|---|---|---|---|---|---|---|---|---|---|
Error | absolute (¢) | +0.0 | -2.0 | +13.7 | +31.2 | +48.7 | -40.5 | -5.0 | +2.5 | -28.3 | -29.6 |
relative (%) | +0 | -2 | +14 | +31 | +49 | -41 | -5 | +2 | -28 | -30 | |
Steps (reduced) |
12 (0) |
19 (7) |
28 (4) |
34 (10) |
42 (6) |
44 (8) |
49 (1) |
51 (3) |
54 (6) |
58 (10) |
12edo achieved its position because it is the smallest equal division of the octave (edo) which can seriously claim to represent 5-limit harmony, and because as 1/12 Pythagorean comma (approximately 1/11 syntonic comma or full schisma) meantone, it represents meantone. It divides the octave into twelve equal parts, each of exactly 100 cents each unless octave shrinking or stretching is employed. It has a fifth which is quite good at two cents flat. It has a major third which is 13+2/3 cents sharp, which works well enough for some styles of music and is not really adequate for others, and a minor third which is flat by even more, 15+2/3 cents. It is probably not an accident that as tuning in European music became increasingly close to 12ET, the style of the music changed so that the defects of 12ET appeared less evident, though it should be borne in mind that in actual performance these are often reduced by the tuning adaptations of the performers.
The seventh partial (7/4) is "represented" by an interval which is sharp by over 31 cents, and stands out distinctly from the rest of the chord in a tetrad. Such tetrads are often used as dominant seventh chords in functional harmony, for which the 5-limit JI version would be 1/1 - 5/4 - 3/2 - 16/9, and while 12ET officially supports septimal meantone via the val ⟨12 19 28 34], its credentials in the 7-limit department are distinctly cheesy. It cannot be said to represent 11 or 13 at all, though it does a quite credible 17 and an even better 19. Nevertheless its relative tuning accuracy is quite high, and 12edo is the fourth zeta integral edo.
In terms of the kernel, which is to say the commas it tempers out, it tempers out the Pythagorean comma, 3^{12}/2^{19}, the Didymus comma, 81/80, the diesis, 128/125, the diaschisma, 2048/2025, the Archytas comma, 64/63, the septimal quartertone, 36/35, the jubilisma, 50/49, the septimal semicomma, 126/125, and the septimal kleisma, 225/224. Each of these affects the structure of 12ET in specific ways, and tuning systems which share the comma in question will be similar to 12ET in precisely those ways.
12edo is the largest equal division of the octave which uniquely patently alternates with an *ed(9/8) in a wtn, and it also contains 2edo, 3edo, 4edo and 6edo as subsets. 12edo is the 5th highly melodic EDO, 12 being both a superabundant and a highly composte number.
Intervals
Steps | Cents | Interval | Approximate JI Ratios* | ||
---|---|---|---|---|---|
0 | 0 | unison | P1 | D | 1/1 |
1 | 100 | aug 1sn, minor 2nd | A1, m2 | D#, Eb | 15/14, 16/15, 17/16, 18/17, 21/20, 25/24, 28/27 |
2 | 200 | major 2nd | M2 | E | 8/7, 9/8, 10/9, 17/15, 19/17 |
3 | 300 | minor 3rd | m3 | F | 7/6, 6/5, 19/16 |
4 | 400 | major 3rd | M3 | F# | 5/4, 9/7 |
5 | 500 | perfect 4th | P4 | G | 4/3 |
6 | 600 | aug 4th, dim 5th | A4, d5 | G#, Ab | 7/5, 10/7, 17/12, 24/17 |
7 | 700 | perfect 5th | P5 | A | 3/2 |
8 | 800 | minor 6th | m6 | Bb | 8/5, 14/9 |
9 | 900 | major 6th | M6 | B | 5/3, 12/7, 32/19 |
10 | 1000 | minor 7th | m7 | C | 7/4, 9/5, 16/9 |
11 | 1100 | major 7th | M7 | C# | 15/8, 17/9, 28/15, 40/21, 48/25, 27/14 |
12 | 1200 | perfect 8ve | P8 | D | 2/1 |
* based on treating 12edo as a 2.3.5.7.17.19 subgroup temperament; other approaches are possible.
JI approximation
15-odd-limit interval mappings
The following table shows how 15-odd-limit intervals are represented in 12edo. Prime harmonics are in bold; inconsistent intervals are in italic.
Interval, complement | Error (abs, ¢) |
---|---|
4/3, 3/2 | 1.955 |
9/8, 16/9 | 3.910 |
13/11, 22/13 | 10.790 |
16/15, 15/8 | 11.731 |
5/4, 8/5 | 13.686 |
6/5, 5/3 | 15.641 |
7/5, 10/7 | 17.488 |
14/11, 11/7 | 17.508 |
10/9, 9/5 | 17.596 |
15/14, 28/15 | 19.443 |
14/13, 13/7 | 28.298 |
8/7, 7/4 | 31.174 |
7/6, 12/7 | 33.129 |
11/10, 20/11 | 34.996 |
9/7, 14/9 | 35.084 |
18/13, 13/9 | 36.618 |
15/11, 22/15 | 36.951 |
13/12, 24/13 | 38.573 |
16/13, 13/8 | 40.528 |
13/10, 20/13 | 45.786 |
11/9, 18/11 | 47.408 |
15/13, 26/15 | 47.741 |
11/8, 16/11 | 48.682 |
12/11, 11/6 | 49.323 |
Selected 19-limit intervals
An expanded version of the above, including some higher-limit intervals:
Regular temperament properties
Subgroup | Comma list | Mapping | Optimal 8ve stretch (¢) |
Tuning error | |
---|---|---|---|---|---|
Absolute (¢) | Relative (%) | ||||
2.3 | [-19 12⟩ | [⟨12 19]] | +0.617 | 0.617 | 0.617 |
2.3.5 | 81/80, 128/125 | [⟨12 19 28]] | -1.56 | 3.11 | 3.11 |
2.3.5.7 | 36/35, 50/49, 64/63 | [⟨12 19 28 34]] | -3.95 | 4.92 | 4.94 |
2.3.5.7.17 | 36/35, 50/49, 51/49, 64/63 | [⟨12 19 28 34 49]] | -2.92 | 4.86 | 4.87 |
2.3.5.7.17.19 | 36/35, 50/49, 51/49, 57/56, 64/63 | [⟨12 19 28 34 49 51]] | -2.53 | 4.52 | 4.53 |
12ET (12f val) is lower in relative error than any previous edos in the 3-, 5-, 7-, 11-, 13-, and 19-limit. The next ETs doing better in those subgroup are 41, 19, 19, 22, 19/19e, and 19egh, respectively. 12ET is even more prominent in the 2.3.5.7.17.19 subgroup, and the next ET that does this better is 72.
Commas
12edo tempers out the following commas. This assumes val ⟨12 19 28 34 42 44].
Prime limit |
Ratio^{[1]} | Monzo | Cents | Color name | Name(s) |
---|---|---|---|---|---|
3 | (12 digits) | [-19 12⟩ | 23.46 | Lalawa | Pythagorean comma |
5 | 648/625 | [3 4 -4⟩ | 62.57 | Quadgu | Major diesis, diminished comma |
5 | 128/125 | [7 0 -3⟩ | 41.06 | Trigu | Diesis, augmented comma |
5 | 81/80 | [-4 4 -1⟩ | 21.51 | Gu | Syntonic comma, Didymus comma, meantone comma |
5 | 2048/2025 | [11 -4 -2⟩ | 19.55 | Sagugu | Diaschisma |
5 | (16 digits) | [26 -12 -3⟩ | 17.60 | Sasa-trigu | Misty comma |
5 | 32805/32768 | [-15 8 1⟩ | 1.95 | Layo | Schisma |
5 | (98 digits) | [161 -84 -12⟩ | 0.02 | Sepbisa-quadtrigu | Atom |
7 | 36/35 | [2 2 -1 -1⟩ | 48.77 | Rugu | Septimal quartertone |
7 | 50/49 | [1 0 2 -2⟩ | 34.98 | Biruyo | Tritonic diesis, jubilisma |
7 | 64/63 | [6 -2 0 -1⟩ | 27.26 | Ru | Septimal comma, Archytas' comma, Leipziger Komma |
7 | 3125/3087 | [0 -2 5 -3⟩ | 21.18 | Triru-aquinyo | Gariboh |
7 | 126/125 | [1 2 -3 1⟩ | 13.79 | Zotrigu | Septimal semicomma, starling comma |
7 | 4000/3969 | [5 -4 3 -2⟩ | 13.47 | Rurutriyo | Octagar |
7 | (12 digits) | [-9 8 -4 2⟩ | 8.04 | Labizogugu | Varunisma |
7 | 225/224 | [-5 2 2 -1⟩ | 7.71 | Ruyoyo | Septimal kleisma, marvel comma |
7 | 3136/3125 | [6 0 -5 2⟩ | 6.08 | Zozoquingu | Hemimean |
7 | 5120/5103 | [10 -6 1 -1⟩ | 5.76 | Saruyo | Hemifamity |
7 | (16 digits) | [25 -14 0 -1⟩ | 3.80 | Sasaru | Garischisma |
7 | (12 digits) | [-11 2 7 -3⟩ | 1.63 | Latriru-asepyo | Meter |
7 | (12 digits) | [-4 6 -6 3⟩ | 0.33 | Trizogugu | Landscape comma |
11 | 99/98 | [-1 2 0 -2 1⟩ | 17.58 | Loruru | Mothwellsma |
11 | 100/99 | [2 -2 2 0 -1⟩ | 17.40 | Luyoyo | Ptolemisma |
11 | 176/175 | [4 0 -2 -1 1⟩ | 9.86 | Lorugugu | Valinorsma |
11 | 896/891 | [7 -4 0 1 -1⟩ | 9.69 | Saluzo | Pentacircle |
11 | 441/440 | [-3 2 -1 2 -1⟩ | 3.93 | Luzozogu | Werckisma |
11 | 9801/9800 | [-3 4 -2 -2 2⟩ | 0.18 | Bilorugu | Kalisma, Gauss' comma |
13 | 91/90 | [-1 -2 -1 1 0 1⟩ | 19.13 | Thozogu | Superleap |
- ↑ Ratios longer than 10 digits are presented by placeholders with informative hints
Rank-2 temperaments
- List of 12et rank two temperaments by badness
- List of 12et rank two temperaments by complexity
- List of edo-distinct 12f rank two temperaments
- Schismic-Pythagorean equivalence continuum
Periods per octave |
Generator | Temperaments |
---|---|---|
1 | 1\12 | Ripple |
1 | 5\12 | Meantone/dominant |
2 | 1\12 | Srutal/pajara/injera |
3 | 1\12 | Augmented |
4 | 1\12 | Diminished |
6 | 1\12 | Hexe |
Scales
- Main article: List of MOS scales in 12edo
The two most common 12edo MOS scales are meantone[5] and meantone[7].
- Diatonic (meantone) 5L2s 2221221 (generator = 7\12)
- Pentatonic (meantone) 2L3s 22323 (generator = 7\12)
- Diminished 4L4s 12121212 (generator = 1\12, period = 3\12)
Pathological Modes
2 1 1 1 1 2 1 1 1 1 2L 8s MOS
3 1 1 1 1 1 1 1 1 1 1L 9s MOS
2 1 1 1 1 1 1 1 1 1 1 1L 10s MOS
Music
- See also: Category:12edo tracks