| Usually (always?) 64 foot flue stops are acoustic, a combination of 32 and 21 1/3 foot ranks which give an interference tone an octave lower. Cheating! The same effect can be produced by the organist by double pedaling a 32 foot flue stop like subbass or even principal. Why not make a real sub-untersatz, a closed 64 foot 8 Hz producing pipe would be only 9 meters tall, but quite thick, naturally, like 1 m square for the lowest pipes. The problem is the huge amount of air this construction would need (separate blower).
Some (maybe 2 or 3 in the world) organs do have a 64 foot reed stop. It really does not give much of fundamental tone, and the working principal is a round lid, "beater", at the end of a spring, which flaps against an opening at the foot of the pipe. It is more a curiosity and a joke than a serious organ stop. |