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 . This is a ratio of approximately 1:1.0058283805847168, or about 10.06 cents ( Play ). It is derived from the difference in pitch between three 75/64 just augmented seconds ( Play just augmented second ) and one 8/5 just minor sixth ( Play minor sixth ) begun on the same root ((3 × 274.58) - (1 × 813.69) = 823.74 - 813.69 = 10.05 cents).
- Haluska, Jan (2003). The Mathematical Theory of Tone Systems, p.xxix. ISBN 80-88683-28-9.
- "List of Intervals", Huygens-Fokker.org.
- "Semicomma", Xenharmonic.Wikispaces.com.