Mike's post triggers another faint memory.  About Spring, 1965, I
was in a campus building and heard a pipe organ from somewhere in the
building.  Because they were investing a new University President, they
were setting up in a two story building whose bottom floor was the
campus basketball arena and whose upper floor was given over as an
indoor drill area for the ROTC programs.

Having spent enough time in that building over the previous year, I
KNEW there was no organ in that building, pipe or otherwise.  Yet, my
ears clearly told me that there was a pretty powerful organ playing,
and from the range of sound, it was no portable "wimp" either!

It wasn't likely, for a one-evening ceremony, that they would
temporarily install a pipe organ -- logistically it seemed impossible,
so I followed my ears until I found the source - an electronic organ!

You have to remember that at this time, the only types of organ that
I had ever come across were real pipe organs, small reed organs, and
the Hammond electronic organ and variants thereof.  Each had a
characteristic sound, and the technology of that time, no electronic
organ of any make that I had ever heard could duplicate, in any vague
way, the voice character of a real pipe organ -- to say nothing of the
chiff of the pipe as it just begins to sound.

This instrument didn't have the tracker noise, blower noise, or
chiff, but the individual "pipes" were extraordinarily realistic.
It is hard to describe how real it actually sounded, but it was VERY
convincing.  So, being a freshman E.E. student, I tracked down the
installer and started asking questions.

Turns out it was a reasonably local company (Eastern PA) that built
the instrument, and if I remember correctly, in their design phase,
they realized that the sound from a pipe is a combination of the
fundamental, various harmonics, AND the noise of the air flow through
the pipe.  Previous electronic organs certainly generated the
fundamental tone, some -- to varying degrees -- may have added a har-
monic or two, but these designers injected white noise to the signal
to simulate the air flow noise.  WOW, what a difference it made!

So for those out there, if you are synthesizing sounds to emulate an
organ pipe, don't forget to experiment with the injection of various
amounts of white noise to see how it affects the composite signal's
ability to sound like a real pipe.

Harvey Chao

 [ A tolerable calliope sound can be synthesized with only the funda-
 [ mental and third harmonic, plus white noise modulated by the tone.
 [ -- Robbie