12edo: Difference between revisions

12edo achieved its position because it is the smallest number of equal divisions of the octave ([[edo]]) which can seriously claim to represent [[5-limit]] harmony, and because as {{frac|1|12}} Pythagorean comma (approximately {{frac|1|11}} syntonic comma or full schisma) meantone, it represents [[meantone]]. It divides the octave into twelve equal parts, each of exactly 100 [[cent]]s each unless [[stretched and compressed tuning|octave stretching or compression]] is employed. It has a fifth which is quite accurate at two cents flat. It has a major third which is 13.7 cents sharp, which, while reasonable for its size, is unsatisfactory for many (especially among those who come to xenharmony), and a minor third which is flat by even more, 15.6 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 sometimes reduced by the tuning adaptations of the performers. Another change that resulted from the adoption of 12edo is the general detachment from the actual meantone and 5-limit system which originally justified it, with theories such as serialism and much of jazz theory deriving from 12edo's nature as a system itself rather than its underlying temperament structure.

12edo is the basic example of an equidodecatonic scale, or more simply, a 12-[[well temperament]]. It is in the position after 7edo as convergent to a musically "natural" [[golden meantone]] fifth.  

The seventh partial ([[7/4]]) is "represented" by an interval which is sharp by 31 cents, which is why minor sevenths tend to stand 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 [[support]]s septimal meantone via its patent [[val]] of {{val| 12 19 28 34}}, its approximations of 7-limit intervals are not very accurate. 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]].

The commas it tempers out include the Pythagorean comma, [[Pythagorean comma|3¹²/2¹⁹]], the syntonic comma, [[81/80]], the lesser diesis, [[128/125]], the diaschisma, [[2048/2025]], the septimal 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 contains [[2edo]], [[3edo]], [[4edo]], and [[6edo]] as subsets. It is the 5th [[highly composite edo]], 12 being both a superabundant and a highly composite number. 12edo is also the only known edo aside from 2edo that is both [[The Riemann zeta function and tuning|strict zeta]] and highly composite.