22 equal temperament

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In music, 22 equal temperament, called 22-TET, 22-EDO, or 22-ET, is the tempered scale derived by dividing the octave into 22 equal steps (equal frequency ratios). About this soundPlay  Each step represents a frequency ratio of 222, or 54.55 cents (About this soundPlay ).

When composing with 22-ET, one needs to take into account different facts. Considering the 5-limit, there is a difference between 3 fifths and the sum of 1 fourth + 1 major third. It means that, starting from C, there are two A's - one 16 steps and one 17 steps away. There is also a difference between a major tone and a minor tone. In C major, the second note (D) will be 4 steps away. However, in A minor, where A is 6 steps below C, the fourth note (D) will be 9 steps above A, so 3 steps above C. So when switching from C major to A minor, one need to slightly change the note D. These discrepancies arise because, unlike 12-ET, 22-ET does not temper out the syntonic comma of 81/80, and in fact exaggerates its size by mapping it to one step.

Extending 22-ET to the 7-limit, we find the septimal minor seventh (7/4) can be distinguished from the sum of a fifth (3/2) and a minor third (6/5). Also the septimal subminor third (7/6) is different from the minor third (6/5). This mapping tempers out the septimal comma of 64/63, which allows 22-ET to function as a "Superpythagorean" system where four stacked fifths are equated with the septimal major third (9/7) rather than the usual pental third of 5/4. This system is a "mirror image" of septimal meantone in many ways. Instead of tempering the fifth narrow so that intervals of 5 are simple while intervals of 7 are complex, the fifth is tempered wide so that intervals of 7 are simple while intervals of 5 are complex. The enharmonic structure is also reversed: sharps are sharper than flats, similar to Pythagorean tuning, but to a greater degree.

Finally, 22-ET has a good approximation of the 11th harmonic, and is in fact the smallest equal temperament to be consistent in the 11-limit.

The net effect is that 22-ET allows (and to some extent even forces) the exploration of new musical territory, while still having excellent approximations of common practice consonances.


History and use[edit]

The idea of dividing the octave into 22 steps of equal size seems to have originated with nineteenth-century music theorist RHM Bosanquet. Inspired by the division of the octave into 22 unequal parts in the music theory of India, Bosanquet noted that an equal division was capable of representing 5-limit music with tolerable accuracy.[1] In this he was followed in the twentieth century by theorist José Würschmidt, who noted it as a possible next step after 19 equal temperament, and J. Murray Barbour in his survey of tuning history, Tuning and Temperament.[2] Contemporary advocates of 22 equal temperament include music theorist Paul Erlich.

Notation[edit]

22-EDO can be notated several ways. The first, Up/Down Notation, uses ups and downs in addition to sharps and flats. This yields the following chromatic scale:

C, C, C, C,

D, E, E, E, E,

F, F, F, F,

G, G/A, G/A, G/A,

A, B, B, B, B, C

The second, Quarter Tone Notation, uses quarter tone notation to divide the notes of Up/Down Notation. However, some chord spellings may change. This yields the following chromatic scale:

C, Chalf sharp, C/D, Dhalf flat,

D, Dhalf sharp, D/E, Ehalf flat, E,

F, Fhalf sharp, F/G, Ghalf flat,

G, Ghalf sharp, G/A, Ahalf flat,

A, Ahalf sharp, A/B, Bhalf flat, B, C

The third, Porcupine Notation, introduces no new accidentals, but significantly changes chord spellings. In addition, enharmonicities from 12-EDO are no longer valid. This yields the following chromatic scale:

C, C, D, D, D, E, E, E, F, F, F, G, G, G, Gdouble sharp/Adouble flat, A, A, A, B, B, B, C, C

Interval size[edit]

Here are the sizes of some common intervals in this system (intervals that are more than 1/4 of a step, in this case, more than ≈13.5 cents, out of tune):

interval name size (steps) size (cents) midi just ratio just (cents) midi error
octave 22 1200 2:1 1200 0
17:10 wide major sixth 17 927.27 About this soundPlay
 
17:10 918.64 08.63
major sixth 16 872.73 About this soundPlay
 
5:3 884.36 About this soundPlay
 
−11.63
perfect fifth 13 709.09 About this soundPlay
 
3:2 701.95 About this soundPlay
 
+07.14
septendecimal tritone 11 600.00 About this soundPlay
 
17:12 603.00 03.00
septimal tritone 11 600.00 7:5 582.51 About this soundPlay
 
+17.49
11:8 wide fourth 10 545.45 About this soundPlay
 
11:80 551.32 About this soundPlay
 
05.87
15:11 wide fourth 10 545.45 15:11 536.95 About this soundPlay
 
+08.50
perfect fourth 09 490.91 About this soundPlay
 
4:3 498.05 About this soundPlay
 
07.14
septendecimal supermajor third 08 436.36 About this soundPlay
 
22:17 446.36 −10.00
septimal major third 08 436.36 9:7 435.08 About this soundPlay
 
+01.28
undecimal major third 08 436.36 14:11 417.51 About this soundPlay
 
+18.86
major third 07 381.82 About this soundPlay
 
5:4 386.31 About this soundPlay
 
04.49
undecimal neutral third 06 327.27 About this soundPlay
 
11:90 347.41 About this soundPlay
 
−20.14
septendecimal supraminor third 06 327.27 17:14 336.13 About this soundPlay
 
08.86
minor third 06 327.27 6:5 315.64 About this soundPlay
 
+11.63
septendecimal augmented second 05 272.73 About this soundPlay
 
20:17 281.36 08.63
septimal minor third 05 272.73 7:6 266.88 About this soundPlay
 
+05.85
septimal whole tone 04 218.18 About this soundPlay
 
8:7 231.17 About this soundPlay
 
−12.99
septendecimal major second 04 218.18 17:15 216.69 +01.50
whole tone, major tone 04 218.18 9:8 203.91 About this soundPlay
 
+14.27
whole tone, minor tone 03 163.64 About this soundPlay
 
10:90 182.40 About this soundPlay
 
−18.77
neutral second, greater undecimal 03 163.64 11:10 165.00 About this soundPlay
 
01.37
neutral second, lesser undecimal 03 163.64 12:11 150.64 About this soundPlay
 
+13.00
septimal diatonic semitone 02 109.09 About this soundPlay
 
15:14 119.44 About this soundPlay
 
−10.35
diatonic semitone, just 02 109.09 16:15 111.73 About this soundPlay
 
02.64
17th harmonic 02 109.09 17:16 104.95 About this soundPlay
 
+04.13
Arabic lute index finger 02 109.09 18:17 098.95 About this soundPlay
 
+10.14
septimal chromatic semitone 02 109.09 21:20 084.47 About this soundPlay
 
+24.62
chromatic semitone, just 01 054.55 About this soundPlay
 
25:24 070.67 About this soundPlay
 
−16.13
septimal third-tone 01 054.55 28:27 062.96 About this soundPlay
 
08.42
undecimal quarter tone 01 054.55 33:32 053.27 About this soundPlay
 
+01.27
septimal quarter tone 01 054.55 36:35 048.77 About this soundPlay
 
+05.78

See also[edit]

References[edit]

  1. ^ Bosanquet, R.H.M. "On the Hindoo division of the octave, with additions to the theory of higher orders" (Archived 2009-10-22), Proceedings of the Royal Society of London vol. 26 (March 1, 1877, to December 20, 1877) Taylor & Francis, London 1878, pp. 372–384. (Reproduced in Tagore, Sourindro Mohun, Hindu Music from Various Authors, Chowkhamba Sanskrit Series, Varanasi, India, 1965).
  2. ^ Barbour, James Murray, Tuning and temperament, a historical survey, East Lansing, Michigan State College Press, 1953 [c1951].

External links[edit]