Greetings to all!  The summer of '01 provided me some opportunities
in my quest for knowledge about one of my favorite obsessions,
Dutch street organs.  I saw and heard two outstanding examples of
Carl Frei organs at Dutch Village in Holland, Michigan, and another
one at the rally in Eureka Springs, Arkansas.

On one of these organs an access panel was removed revealing some of
the inner workings, including the tremulant.  I could see a pneumatic
device oscillating at a rate of about seven Hertz ("Alpha waves",
anyone?) and which clearly corresponded to the tremolo heard in the
melody ranks.  This tremulant would pulse wind to the pipes by
alternately canceling and drawing whichever of the two melody stops was
in use at a given time.  The tremulant was turned off by another
pneumatic which would force the tremulant pneumatic closed.

An advantage of this approach to controlling the oscillator is that
it can be given a synchronous start.  A book arranged with frequent and
well-placed "trem off" and "trem on" commands and played with tempo at
or near an integral sub-multiple of the trem rate, say one-quarter
(105 beats per minute) or one-sixth (70 beats per minute) gives a
pretty good illusion of metered tremolo.  This effect can be heard
often in the "Dutch Band Organ" recordings.

A problem with these book-playing organs is that occasionally the book
will hang in the keyframe causing an unplanned fermata.  I have seen
operators respond to such a condition by grabbing the book at the
discharge side and tugging.  It seems to me that it might be easier on
the book if one were to clear the jam by briefly unlatching the overarm
(or whatever the hinged top part of the keyframe mechanism is called.)
This procedure is effective, as I have confirmed by experiment. ;-)
Comments, anyone?

I am still looking for the physical dimensions of the 72-key Carl Frei
tracker scale.  Can anyone help?

One other observation:  I'll bet a lot of English speakers like me have
been mispronouncing Carl Frei's last name like "fry."  The announcer at
Dutch Village, a native speaker of Dutch, says it like "free," that is,
with a long "e" and the "i" silent.

Regards,
Doug Mauldin