Adriaan D. Fokker

Adriaan Daniël Fokker (17 Aug 1887, Buitenzorg, Dutch East Indies — 24 Sept 1972, Beekbergen, Netherlands) was a Dutch physicist and music theorist who researched 31-tone equal temperaments and designed several instruments that can play microtonal scales on a generalized keyboard. His best-known instrument, the "Fokker organ," was initially built in 1951 at Teylers Museum, Haarlem and relocated to Muziekgebouw aan 't IJ in Amsterdam, where it's currently owned by the Huygens-Fokker Foundation.