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From: Steve & Anne Price
Date: Tue, 10 Sep 1996 19:09:42 -0500 (CDT)
Subject: blow draw and acoustic

The question was raised how the reeds know which way the wind is
going to know whether to sound. In the newer MS harps they are triggered
with wind direction sensitive microprocessors, but that doesn't account
for the older pre-MS series harmonicas, which actually use an analogue
rather than digital airflow interface. Those older ones used the same
principle that get airplanes off the ground, called "lift," as follows:
They've shaped the reeds to approximate airplane wings which also vibrate
and twist around when the wind hits them, but at a much lower frequency
(but not low enough that you don't get a headache from a couple hours in
the air). The draw reeds work because they've just installed them upside
down. Blow and draw work according to known physical concepts.
Overblows and overdraws operate under no known physical laws.

The reason playing through a P.A. is "acoustic" is that you can
hear it. Why it is considered "unplugged," though, is also beyond any
known physical laws.

s.p. (student of Dr. Science)