72 equal temperament

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search

In music, 72 equal temperament, called twelfth-tone, 72-TET, 72-EDO, or 72-ET, is the tempered scale derived by dividing the octave into twelfth-tones, or in other words 72 equal steps (equal frequency ratios). About this soundPlay  Each step represents a frequency ratio of 722, or 16+23 cents, which divides the 100 cent "halftone" into 6 equal parts (100 ÷ 16+23 = 6) and is thus a "twelfth-tone" (About this soundPlay ). Since 72 is divisible by 1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36, and 72, 72-EDO includes all those equal temperaments. Since it contains so many temperaments, 72-EDO contains at the same time tempered semitones, third-tones, quartertones and sixth-tones, which makes it a very versatile temperament.

This division of the octave has attracted much attention from tuning theorists, since on the one hand it subdivides the standard 12 equal temperament and on the other hand it accurately represents overtones up to the twelfth partial tone, and hence can be used for 11-limit music. It was theoreticized in the form of twelfth-tones by Alois Hába[1] and Ivan Wyschnegradsky,[2][3][4] who considered it as a good approach to the continuum of sound. 72-EDO is also cited among the divisions of the tone by Julián Carrillo, who preferred the sixteenth-tone as an approximation to continuous sound in discontinuous scales.

History and use[edit]

Byzantine music[edit]

The 72 equal temperament is used in Byzantine music theory,[5] dividing the octave into 72 equal moria, which itself derives from interpretations of the theories of Aristoxenos, who used something similar. Although the 72 equal temperament is based on irrational intervals (see above), as is the 12 tone equal temperament mostly commonly used in Western music (and which is contained as a subset within 72 equal temperament), 72 equal temperament, as a much finer division of the octave, is an excellent tuning for both representing the division of the octave according to the diatonic and the chromatic genera in which intervals are based on ratios between notes, and for representing with great accuracy many rational intervals as well as irrational intervals.

Other history and use[edit]

A number of composers have made use of it, and these represent widely different points of view and types of musical practice. These include Alois Hába, Julián Carrillo, Ivan Wyschnegradsky and Iannis Xenakis.[citation needed]

Many other composers use it freely and intuitively, such as jazz musician Joe Maneri, and classically oriented composers such as Julia Werntz and others associated with the Boston Microtonal Society. Others, such as New York composer Joseph Pehrson are interested in it because it supports the use of miracle temperament, and still others simply because it approximates higher-limit just intonation, such as Ezra Sims and James Tenney. There was also an active Soviet school of 72 equal composers, with less familiar names: Evgeny Alexandrovich Murzin, Andrei Volkonsky, Nikolai Nikolsky, Eduard Artemiev, Alexander Nemtin, Andrei Eshpai, Gennady Gladkov, Pyotr Meshchianinov, and Stanislav Kreichi.[citation needed]

The ANS synthesizer uses 72 equal temperament.


The Maneri-Sims notation system designed for 72-et uses the accidentals and for 112-tone down and up (1 step = 16+23 cents), Half down arrow.png and Half up arrow.png for 16 down and up (2 steps = 33+13 cents), and Sims flagged arrow down.svg and Sims flagged arrow up.svg for 14 up and down (3 steps = 50 cents).

They may be combined with the traditional sharp and flat symbols (6 steps = 100 cents) by being placed before them, for example: Half down arrow.png or Sims flagged arrow up.svg, but without the intervening space. A 13 tone may be one of the following Sims flagged arrow up.svg, Sims flagged arrow down.svg, Half down arrow.png, or Half up arrow.png (4 steps = 66+23) while 5 steps may be Half up arrow.pngSims flagged arrow up.svg, , or (83+13 cents).

Interval size[edit]

Below are the sizes of some intervals (common and esoteric) in this tuning. For reference, differences of less than 5 cents are melodically imperceptible to most people:

Interval Name Size (steps) Size (cents) MIDI Just Ratio Just (cents) MIDI Error
octave 72 1200 2:1 1200 0
perfect fifth 42 700 About this soundplay  3:2 701.96 About this soundplay  −1.96
septendecimal tritone 36 600 About this soundplay  17:12 603.00 −3.00
septimal tritone 35 583.33 About this soundplay  7:5 582.51 About this soundplay  +0.82
tridecimal tritone 34 566.67 About this soundplay  18:13 563.38 +3.28
11th harmonic 33 550 About this soundplay  11:8 551.32 About this soundplay  −1.32
(15:11) augmented fourth 32 533.33 About this soundplay  15:11 536.95 About this soundplay  −3.62
perfect fourth 30 500 About this soundplay  4:3 498.04 About this soundplay  +1.96
septimal narrow fourth 28 466.66 About this soundplay  21:16 470.78 About this soundplay  −4.11
17:13 narrow fourth 17:13 464.43 +2.24
tridecimal major third 27 450 About this soundplay  13:10 454.21 About this soundplay  −4.21
septendecimal supermajor third 22:17 446.36 +3.64
septimal major third 26 433.33 About this soundplay  9:7 435.08 About this soundplay  −1.75
undecimal major third 25 416.67 About this soundplay  14:11 417.51 About this soundplay  −0.84
major third 23 383.33 About this soundplay  5:4 386.31 About this soundplay  −2.98
tridecimal neutral third 22 366.67 About this soundplay  16:13 359.47 +7.19
neutral third 21 350 About this soundplay  11:9 347.41 About this soundplay  +2.59
septendecimal supraminor third 20 333.33 About this soundplay  17:14 336.13 −2.80
minor third 19 316.67 About this soundplay  6:5 315.64 About this soundplay  +1.03
quasi-tempered minor third 18 300 About this soundplay  25:21 301.85 -1.85
tridecimal minor third 17 283.33 About this soundplay  13:11 289.21 About this soundplay  −5.88
septimal minor third 16 266.67 About this soundplay  7:6 266.87 About this soundplay  −0.20
tridecimal 54 tone 15 250 About this soundplay  15:13 247.74 +2.26
septimal whole tone 14 233.33 About this soundplay  8:7 231.17 About this soundplay  +2.16
septendecimal whole tone 13 216.67 About this soundplay  17:15 216.69 −0.02
whole tone, major tone 12 200 About this soundplay  9:8 203.91 About this soundplay  −3.91
whole tone, minor tone 11 183.33 About this soundplay  10:9 182.40 About this soundplay  +0.93
greater undecimal neutral second 10 166.67 About this soundplay  11:10 165.00 About this soundplay  +1.66
lesser undecimal neutral second 9 150 About this soundplay  12:11 150.64 About this soundplay  −0.64
greater tridecimal 23 tone 8 133.33 About this soundplay  13:12 138.57 About this soundplay  −5.24
great limma 27:25 133.24 About this soundplay  +0.09
lesser tridecimal 23 tone 14:13 128.30 About this soundplay  +5.04
septimal diatonic semitone 7 116.67 About this soundplay  15:14 119.44 About this soundplay  −2.78
diatonic semitone 16:15 111.73 About this soundplay  +4.94
greater septendecimal semitone 6 100 About this soundplay  17:16 104.95 About this soundplay  -4.95
lesser septendecimal semitone 18:17 98.95 About this soundplay  +1.05
septimal chromatic semitone 5 83.33 About this soundplay  21:20 84.47 About this soundplay  −1.13
chromatic semitone 4 66.67 About this soundplay  25:24 70.67 About this soundplay  −4.01
septimal third-tone 28:27 62.96 About this soundplay  +3.71
septimal quarter tone 3 50 About this soundplay  36:35 48.77 About this soundplay  +1.23
septimal diesis 2 33.33 About this soundplay  49:48 35.70 About this soundplay  −2.36
undecimal comma 1 16.67 About this soundplay  100:99 17.40 −0.73

Although 12-ET can be viewed as a subset of 72-ET, the closest matches to most commonly used intervals under 72-ET are distinct from the closest matches under 12-ET. For example, the major third of 12-ET, which is sharp, exists as the 24-step interval within 72-ET, but the 23-step interval is a much closer match to the 5:4 ratio of the just major third.

12-ET has a very good approximation for the perfect fifth (third harmonic), especially for such a small number of steps per octave, but compared to the equally-tempered versions in 12-ET, the just major third (fifth harmonic) is off by about a sixth of a step, the seventh harmonic is off by about a third of a step, and the eleventh harmonic is off by about half of a step. This suggests that if each step of 12-ET were divided in six, the fifth, seventh, and eleventh harmonics would now be well-approximated, while 12-ET's excellent approximation of the third harmonic would be retained. Indeed, all intervals involving harmonics up through the 11th are matched very closely in 72-ET; no intervals formed as the difference of any two of these intervals are tempered out by this tuning system. Thus 72-ET can be seen as offering an almost perfect approximation to 7-, 9-, and 11-limit music. When it comes to the higher harmonics, a number of intervals are still matched quite well, but some are tempered out. For instance, the comma 169:168 is tempered out, but other intervals involving the 13-th harmonic are distinguished.

Unlike tunings such as 31-ET and 41-ET, 72-ET contains many intervals which do not closely match any small-number (<16) harmonics in the harmonic series.

Scale diagram[edit]

12-tone About this soundPlay  and 72-tone About this soundPlay  regular diatonic scales notated with the Maneri-Sims system

Because 72-EDO contains 12-EDO, the scale of 12-EDO is in 72-EDO. However, the true scale can be approximated better by other intervals.

See also[edit]


  1. ^ A. Hába: "Harmonické základy ctvrttónové soustavy". German translation: "Neue Harmonielehre des diatonischen, chromatischen Viertel-, Drittel-, Sechstel- und Zwölftel-tonsystems" by the author. Fr. Kistner & C.F.W. Siegel, Leipzig, 1927. Universal, Wien, 1978. Revised by Erich Steinhard, "Grundfragen der mikrotonalen Musik"; Bd. 3, Musikedition Nymphenburg 2001, Filmkunst-Musikverlag, München, 251 pages.
  2. ^ I. Wyschnegradsky: "L'ultrachromatisme et les espaces non octaviants", La Revue Musicale no. 290–291, pp. 71–141, Ed. Richard-Masse, Paris, 1972
  3. ^ La Loi de la Pansonorité (Manuscript, 1953), Ed. Contrechamps, Geneva, 1996. Preface by Pascale Criton, edited by Franck Jedrzejewski. ISBN 978-2-940068-09-8
  4. ^ Une philosophie dialectique de l'art musical (Manuscript, 1936), Ed. L'Harmattan, Paris, 2005, edited by Franck Jedrzejewski. ISBN 978-2-7475-8578-1.
  5. ^ [1] G. Chryssochoidis, D. Delviniotis and G. Kouroupetroglou, "A semi-automated tagging methodology for Orthodox Ecclesiastic Chant Acoustic corpora", Proceedings SMC'07, 4th Sound and Music Computing Conference, Lefkada, Greece (11–13 July 2007).

External links[edit]