Syntonic Comma

In music theory, the syntonic comma, also known as the chromatic diesis, the comma of Didymus, the Ptolemaic comma, or the diatonic comma is a small comma type interval between two musical notes, equal to the frequency ratio 81:80, or around 21.51 cents. Two notes that differ by this interval would sound different from each other even to untrained ears, 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 referred to as a "comma of Didymus" because it is the amount by which Didymus corrected the Pythagorean major third to a just major third (81:64 or 407.82 cents - 21.51 = 386.31 cents or 5:4).

Composer Ben Johnston uses a "−" as an accidental to indicate a note is lowered 21.51 cents, or a "+" to indicate a note is raised 21.51 cents.

Read more about Syntonic CommaRelationships, Syntonic Comma in The History of Music, Comma Pump

Other articles related to "syntonic, syntonic comma, comma, commas":

Syntonic Temperament
... The syntonic temperament is a system of musical tuning in which the frequency ratio of each musical interval is a product of powers of an octave and a tempered perfect fifth, with the width of the ... Alternatively put, the syntonic temperament generates all non-octave intervals from a stack of tempered perfect fifths and tempers the syntonic comma to unison ... The syntonic temperament can be viewed as a systematic extension of the meantone temperament beyond the range imposed by the meantone temperament's ...
Syntonic Comma - Comma Pump
... The syntonic comma arises in the "comma pump" sequence such as C G D A E C, when each interval from one note to the next is played with just intonation tuning ... These multiply together to give which is the syntonic comma (you multiply ratios when you stack musical intervals like that) ... So in that sequence, the second C is sharper than the first C by a syntonic comma ...
Comma (music) - Tempering of Commas
... Commas are frequently used in the description of musical temperaments, where they describe distinctions between musical intervals that are eliminated by that tuning ... A comma can be viewed as the distance between two musical intervals ... When a given comma is tempered out in a tuning system, the ability to distinguish between those two intervals in that tuning is eliminated ...
Comma (music) - Commas in Different Contexts
... Notice that the Pythagorean comma (PC) and the syntonic comma (SC) are basic intervals which can be used as yardsticks to define some of the other commas ... For instance, the difference between them is a small comma called schisma ... Name of comma Alternative Name Definitions Size Difference between semitones Difference between commas Difference between Cents Ratio Interval 1 Interval 2 Schisma ...

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