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). Each step represents a frequency ratio of , or which divides the 100 cent
12 EDO "
halftone
Halftone is the reprographic technique that simulates continuous tone, continuous-tone imagery through the use of dots, varying either in size or in spacing, thus generating a gradient-like effect.Campbell, Alastair. ''The Designer's Lexicon''. ...
" into 6 equal parts (100 cents ÷ 6 steps, exactly) and is thus a "twelfth-tone" (). 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 and
Ivan Wyschnegradsky, 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 (96 EDO) as an approximation to continuous sound in discontinuous scales.
History and use
Byzantine music
The 72 equal temperament is used in
Byzantine music theory,
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 (12 EDO) 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
ancient Greek
Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...
diatonic
Diatonic and chromatic are terms in music theory that are used to characterize scales. The terms are also applied to musical instruments, intervals, chords, notes, musical styles, and kinds of harmony. They are very often used as a pair ...
and the
chromatic genera
Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...
in which intervals are based on
ratio
In mathematics, a ratio () shows how many times one number contains another. For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lemons is eight to six (that is, 8:6, which is equivalent to the ...
s between notes, and for representing with great accuracy many rational intervals as well as irrational intervals.
Other history and use
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.
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 EDO composers, with less familiar names:
Evgeny Alexandrovich Murzin,
Andrei Volkonsky,
Nikolai Nikolsky,
Eduard Artemiev,
Alexander Nemtin,
Andrei Eshpai,
Gennady Gladkov
Gennady Igorevich Gladkov (; 18 February 1935 – 16 October 2023) was a Soviet and Russian composer. He composed music for some of the most famous Soviet movies and cartoons, most notably ''The Bremen Town Musicians (1969 film), The Bremen Town ...
,
Pyotr Meshchianinov, and
Stanislav Kreichi.
The
ANS synthesizer uses 72 equal temperament.
Notation
The Maneri-Sims notation system designed for 72 EDO uses the
accidentals and for down and up (1 step and for and up (2 steps and and for
septimal up and down (3 steps
They may be combined with the traditional sharp and flat symbols (6 steps = 100 cents) by being placed before them, for example: or , but without the intervening space. A tone may be one of the following , , , or (4 steps = ) while 5 steps may be , , or ( cents).
Interval size
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, and approaching the limits of feasible tuning accuracy for acoustic instruments. Note that it is ''not possible'' for any pitch to be further than from its nearest 72 EDO note, since the step size between them is Hence for the sake of comparison, pitch errors of about 8 cents are (for this fine a tuning) poorly matched, whereas the practical limit for tuning any acoustical instrument is at best about 2 cents, which would be very good match in the table – this even applies to electronic instruments if they produce notes that show any audible trace of
vibrato.
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*
*
Although
12 EDO can be viewed as a subset of 72 EDO, the closest matches to most commonly used intervals under 72 EDO are distinct from the closest matches under 12 EDO. For example, the
major third
In music theory, a third is a Interval (music), musical interval encompassing three staff positions (see Interval (music)#Number, Interval number for more details), and the major third () is a third spanning four Semitone, half steps or two ...
of 12 EDO, which is sharp, exists as the 24 step interval within 72 EDO, but the 23 step interval is a much closer match to the 5:4 ratio of the just major third.
12 EDO has a very good approximation for the
perfect fifth
In music theory, a perfect fifth is the Interval (music), musical interval corresponding to a pair of pitch (music), pitches with a frequency ratio of 3:2, or very nearly so.
In classical music from Western culture, a fifth is the interval f ...
(third harmonic), especially for such a small number of steps per octave, but compared to the equally-tempered versions in 12 EDO, 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 EDO were divided in six, the fifth, seventh, and eleventh harmonics would now be well-approximated, while 12 EDO‑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 EDO; no intervals formed as the difference of any two of these intervals are tempered out by this tuning system. Thus, 72 EDO 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 13th harmonic are distinguished.
Unlike tunings such as
31 EDO and
41 EDO, 72 EDO contains many intervals which do not closely match any small-number (< 16) harmonics in the harmonic series.
Scale diagram
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
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Musical temperament
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Equal temperament
An equal temperament is a musical temperament or Musical tuning#Tuning systems, tuning system that approximates Just intonation, just intervals by dividing an octave (or other interval) into steps such that the ratio of the frequency, frequencie ...
References
External links
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* — symbols for Maneri-Sims notation and others
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{{Byzantine music
Equal temperaments
Byzantine music
Microtonality