After 1945 Fokker continued musical composition and other musical activities.
He concentrated more and more on tuning theory, especially in relation to just
intonation and 31-tone tuning. He began a larger enterprise of instrument
building, namely an organ with the full scale of 31 tones per octave. He
secured enough financial aid for its construction, and the organ - of his own
design - was installed in Teyler's Museum in 1950. It is now usually called the
"Fokker organ". It has a main console with two 31-tone manuals and a pedal
keyboard, and an additional console with 12-tone keyboards on which portions of
the 31-tone scale can be played. The first organist was Paul Christiaan van
Westering. The first concert on the new organ was given on 10 September 1951,
with compositions by Jan Pieterszoon Sweelinck, Paul Christiaan van Westering
and Jan van Dijk. Concerts involving the organ
took place frequently during the period 1951-1955, featuring both newly-written
31-tone music on the main keyboard and early music on the meantone option of
the additional, 12-tone keyboard. Since then concerts were given on each first
Sunday of the month, except in January.
The disposition of the organ is
Manual I C-g''' (143 tones, 319 keys): Quintaten 8', Prestant 4';
Manual II C-g''' (143 tones, 319 keys): Salicionaal 8', Chimney flute 4';
Pedal C-f (45 tones and keys): Sub-bass 16', Stopped flute 8' (transm.)
Couplings: (P + I); (P + II); (I + II). Pitch: a' = 440 Hz.
The disposition on the additional console with a normal 12-tone keyboard is the
same, except in the Pedal. Because it has one octave more, Stopped flute 8' was
left away. The 12-tone keyboard is connected to the organ in a special way. By
means of nine push buttons nine 12-tone selections out of the 31 tones per
octave can be connected to the manual. Eight of them are fixed and for one
tones can be selected at random with switches. The fixed selections are
Euler-Fokker genera with fifths, major thirds and harmonic sevenths making
scales with 12 tones per octave: [3³.5²], [3².5³],
[5³.7²], [3³.7²], [5².7³], [3².5.7],
In the programmable selection the meantone scale can be set, with E and G. It provides the notes as
used and conceived by the 17th and 18th century composers and it thereby
restores the ancient beauty of their creations. As Fokker said: "this is the
console looking back to the classical past." The other console with the 31-tone
keyboards is "the console looking to the future."
The organ was removed from the museum in 2000, then stored at the organ builder and
renovated from 2008 to 2009 and built up again in the BAM Zaal of the Muziekgebouw aan 't IJ.
For sound examples of the Fokker organ, go to the
Schematic representation of the keyboard design of the Fokker organ.
A.D. Fokker: About the construction of the 31-tone organ
Photos after the renovation
Renovation Fokker organ
In 2008/2009 the Fokker organ was completely renovated and was placed in the Small Hall of the Muziekgebouw aan 't IJ. Read all about the renovation of the Fokker-organ here.