Semicomma

Semicomma on C <phonos file="Semicomma on C.mid">Play</phonos>.

The semicomma, also Fokker's comma (after 31-TET pioneer Adriaan Fokker), is type of small musical interval, or comma, in microtonal music equivalent to 2109375:2097152, or $3^3\cdot5^7:2^{21}$. This is a ratio of approximately 1:1.0058283805847168, or about 10.06 cents (<phonos file="Semicomma on C.mid">Play</phonos>). It is derived from the difference in pitch between three 75/64 just augmented seconds (<phonos file="Just augmented second on C.mid">Play just augmented second</phonos>) and one 8/5 just minor sixth (<phonos file="Just minor sixth on C.mid">Play minor sixth</phonos>) begun on the same root ((3 × 274.58) - (1 × 813.69) = 823.74 - 813.69 = 10.05 cents).

See also

• Septimal kleisma
• Septimal semicomma