{ Ref. Christian Tedesco in 210520 MMDigest ]

Audsley, in his book, "The Art of Organ-Building", describes such
a contraption on page 497 of volume II: "In constructing our own
Chamber Organ we found great difficulty in accommodating the larger
pipes of the Principale, 16 ft., ... We were perfectly successful,
by the introcution of simple appliances of a pneumatic character,
in making the CCC and DDD pipes serve also fir the CCC# and DDD#
notes; ...". 

He shows a nice cross section illustration of it -- but it's not too
easy to build this, I'd say.

H. M. Mueller
Grafing, Germany