In our earlier days at Stinson Band Organ we built a series of organs
based on the Wurlitzer Caliola.  These contained large open pipes
voiced at eight inches W.G. wind pressure in a very confined case.

When tuning a large pipe on some of the units the large pipe on the
other side of the case would draw when tuning.  When tuning the pipe
you could feel the air traveling in the other pipe and it was necessary
to block the second pipe to tune correctly.

In one case we decided to see what it would take to stop this and so
we cut side windows in the instrument much like the Wurlitzer Caliola
and the problem was solved.  I have often wondered if the side windows
in the Wurlitzer were for sound dispersion or if they might have had
the same problem.

Don Stinson - Stinson Band Organ Company Inc.
http://www.stinsonbandorgans.com/