41 equal temperament

In music, 41 equal temperament, abbreviated 41-TET, 41-EDO, or 41-ET, is the tempered scale derived by dividing the octave into 41 equally sized steps (equal frequency ratios). Play  Each step represents a frequency ratio of 21/41, or 29.27 cents (Play ), an interval close in size to the septimal comma. 41-ET can be seen as a tuning of the schismatic,[1] magic and miracle[2] temperaments. It is the second smallest equal temperament, after 29-ET, whose perfect fifth is closer to just intonation than that of 12-ET. In other words, is a better approximation to the ratio than either or .

History and use

Although 41-ET has not seen as wide use as other temperaments such as 19-ET or 31-ET , pianist and engineer Paul von Janko built a piano using this tuning, which is on display at the Gemeentemuseum in The Hague.[3] 41-ET can also be seen as an octave-based approximation of the Bohlen–Pierce scale.

41-ET guitars have been built, notably by Yossi Tamim. To make a more playable 41-ET guitar, an approach called "The Kite Tuning" omits every-other fret (in other words, 41 frets per two octaves or 20.5 frets per octave) while tuning adjacent strings to an odd number of steps of 41.[4] Thus, any two adjacent strings together contain all the pitch classes of the full 41-ET system. The Kite Guitar's main tuning uses 13 steps of 41-ET (which approximates a 5/4 ratio) between strings. With that tuning, all simple ratios of odd limit 9 or less are available at spans at most only 4 frets.

41-ET is also a subset of 205-ET, for which the keyboard layout of the Tonal Plexus is designed.

Interval size

Here are the sizes of some common intervals (shaded rows mark relatively poor matches):

interval name size (steps) size (cents) midi just ratio just (cents) midi error
octave 41 1200 2:1 1200 0
harmonic seventh 33 965.85 Play  7:4 968.83 Play  −2.97
perfect fifth 24 702.44 Play  3:2 701.96 Play  +0.48
septimal tritone 20 585.37 Play  7:5 582.51 Play  +2.85
11:8 wide fourth 19 556.10 Play  11:8 551.32 Play  +4.78
15:11 wide fourth 18 526.83 Play  15:11 536.95 Play  −10.12
27:20 wide fourth 18 526.83 Play  27:20 519.55 Play  +7.28
perfect fourth 17 497.56 Play  4:3 498.04 Play  −0.48
septimal narrow fourth 16 468.29 Play  21:16 470.78 Play  −2.48
septimal major third 15 439.02 Play  9:7 435.08 Play  +3.94
undecimal major third 14 409.76 Play  14:11 417.51 Play  −7.75
Pythagorean major third 14 409.76 Play  81:64 407.82 Play  +1.94
major third 13 380.49 Play  5:4 386.31 Play  −5.83
tridecimal neutral third, inverted 13th harmonic 12 351.22 Play  16:13 359.47 Play  −8.25
undecimal neutral third 12 351.22 Play  11:9 347.41 Play  +3.81
minor third 11 321.95 Play  6:5 315.64 Play  +6.31
Pythagorean minor third 10 292.68 Play  32:27 294.13 Play  −1.45
tridecimal minor third 10 292.68 Play  13:11 289.21 Play  +3.47
septimal minor third 9 263.41 Play  7:6 266.87 Play  −3.46
septimal whole tone 8 234.15 Play  8:7 231.17 Play  +2.97
diminished third 8 234.15 Play  256:225 223.46 Play  +10.68
whole tone, major tone 7 204.88 Play  9:8 203.91 Play  +0.97
whole tone, minor tone 6 175.61 Play  10:9 182.40 Play  −6.79
lesser undecimal neutral second 5 146.34 Play  12:11 150.64 Play  −4.30
septimal diatonic semitone 4 117.07 Play  15:14 119.44 Play  −2.37
Pythagorean chromatic semitone 4 117.07 Play  2187:2048 113.69 Play  +3.39
diatonic semitone 4 117.07 Play  16:15 111.73 Play  +5.34
Pythagorean diatonic semitone 3 87.80 Play  256:243 90.22 Play  −2.42
20:19 wide semitone 3 87.80 Play  20:19 88.80 Play  −1.00
septimal chromatic semitone 3 87.80 Play  21:20 84.47 Play  +3.34
chromatic semitone 2 58.54 Play  25:24 70.67 Play  −12.14
28:27 wide semitone 2 58.54 Play  28:27 62.96 Play  −4.42
septimal comma 1 29.27 Play  64:63 27.26 Play  +2.00

As the table above shows, the 41-ET both distinguishes between and closely matches all intervals involving the ratios in the harmonic series up to and including the 10th overtone. This includes the distinction between the major tone and minor tone (thus 41-ET is not a meantone tuning). These close fits make 41-ET a good approximation for 5-, 7- and 9-limit music.

41-ET also closely matches a number of other intervals involving higher harmonics. It distinguishes between and closely matches all intervals involving up through the 12th overtones, with the exception of the greater undecimal neutral second (11:10). Although not as accurate, it can be considered a full 15-limit tuning as well.

Tempering

Intervals not tempered out by 41-ET include the diesis (128:125), septimal diesis (49:48), septimal sixth-tone (50:49), septimal comma (64:63), and the syntonic comma (81:80).

41-ET tempers out the 100:99 ratio, which is the difference between the greater undecimal neutral second and the minor tone, as well as the septimal kleisma (225:224), 1029:1024 (the difference between three intervals of 8:7 the interval 3:2), and the small diesis (3125:3072).

References
  1. "Schismic Temperaments ", Intonation Information.
  2. "Lattices with Decimal Notation", Intonation Information.
  3. Dirk de Klerk "Equal Temperament", Acta Musicologica, Vol. 51, Fasc. 1 (Jan. - Jun., 1979), pp. 140-150
  4. "The Kite Guitar ", Xenharmonic Wiki.
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