Syntonic comma

Syntonic comma (81:80) on C

Helmholtz-Ellis notation

In music theory, the syntonic comma, also known as the chromatic diesis, the Didymean comma, the Ptolemaic comma, or the diatonic comma^[2] is a small comma type interval between two musical notes, equal to the frequency ratio 81:80 (= 1.0125) (around 21.51 cents). Two notes that differ by this interval would sound different from each other even to untrained ears,^[3] but would be close enough that they would be more likely interpreted as out-of-tune versions of the same note than as different notes. The comma is also referred to as a Didymean comma because it is the amount by which Didymus corrected the Pythagorean major third (81:64, around 407.82 cents)^[4] to a just major third (5:4, around 386.31 cents).

The word "comma" came via Latin from Greek κόμμα, from earlier *κοπ-μα = "a thing cut off".

^ Cite error: The named reference Fonville was invoked but never defined (see the help page).
^ Johnston B. (2006). "Maximum Clarity" and Other Writings on Music, edited by Bob Gilmore. Urbana: University of Illinois Press. ISBN 0-252-03098-2.
^ "Sol-Fa – The Key to Temperament" Archived 2005-02-08 at the Wayback Machine, BBC.
^ Cite error: The named reference Lloyd was invoked but never defined (see the help page).

[Fonville-1] Cite error: The named reference Fonville was invoked but never defined (see the help page).

[2] Johnston B. (2006). "Maximum Clarity" and Other Writings on Music, edited by Bob Gilmore. Urbana: University of Illinois Press. ISBN 0-252-03098-2.

[3] "Sol-Fa – The Key to Temperament" Archived 2005-02-08 at the Wayback Machine, BBC.

[Lloyd-4] Cite error: The named reference Lloyd was invoked but never defined (see the help page).

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