After several pilot attempts, initiated by Zeb Vance who taught me
about his Aeolian regulator, I have built a set of pressure regulators
for my organ project.  The final design is described in a new article
at the MMD Tech site [URL below].

A specific feature in this regulator type is a small balancing bellows,
the interior of which is normally connected to atmosphere.  A second
use for this little bellows comes when you feed it with an externally
supplied control pressure that will then modify the regulator output
pressure.  When this control is a pulse train of suitable frequency the
regulator will operate as a tremulant.

A particular merit of this principle, distinguishing it from
conventional tremulants, is that it avoids power consumptive and noisy
periodic air dumps.  Instead, the output pressure is actively
controlled to pulsate.  An oscillator to generate such a control
signal, made from two pouch operated valves arranged into a feedback
circuit is also described.  This oscillator is believed to be an
innovation in the art of organ building.

Johan Liljencrants
Stockholm, Sweden

 [ Thanks, Johan.  I put the article and photos at
 [   http://mmd.foxtail.com/Tech/
 [   http://mmd.foxtail.com/Tech/tremreg.htm
 [ -- Robbie