The Wurlitzer company made a few sets of 32-foot Diaphone pipes where
each resonator was set up with flap valve doors so they only had six
pipes for the bottom octave -- each pipe could play two notes. There is
an operating set of these Wood Diaphone pipes in the Berkeley Community
Theater organ in Berkeley, California.

Bill Klinger
Flippin, Arkansas

 [ More at http://www.organstops.org/d/Diaphone.html
 [ and https://norcaltos.org/photo-gallery
 [ and https://norcaltos.org/wood-diaphones
 [ -- Robbie