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1.307 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 ¶