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1.306 syntonic comma
ES: coma sintónica, coma de Dídimo, I: comma sintonico (o didimico), F: comma syntonique, D: syntonisches Komma, NL: syntonische komma, DK: syntonisk komma, S: syntoniskt komma, FI: syntoninen komma, terssien taajuusero luonnollisessa ja Pytagorisessa viritysjärjestelmässä.
Named after Ptolemy’s syntonic diatonic genus. Originally, the difference by which the ditone exceeds the pure major third obtained by Pythagorean tuning: (9:8)^2 / (5:4) = 81:80, or 21.5 cents.1
Modern acoustics theory defines it as the interval by which four fifths exceed the sum of two octaves plus a major third: (3:2)^4 / ((2:1)^2 * (5:4)).
This comma is also known as the comma of Didymus, or didymic comma.
See also
Footnotes
(1)
Addition and subtraction of intervals are represented in the arithmetic expressions by multiplication and division, respectively.