Johan Liljencrants writes in Digest.00.04.03:

>  3.  Inward beating reeds, as found in the oboe, bassoon, clarinet,
> saxophone, and organ reed pipe.  The wind supply tends to _close_ the
> reed passage.  The frequency is complexly related to the natural
> frequency and is also much dependent on pressure.  Inward beating
> reeds are used with a resonator, and the coupling of the resonance to
> the downwind side of the reed is _strong_ because of the large exposed
> reed area.  The reed is dominantly a _stiffness; [load? resistance?]
> the tone fundamental frequency is slightly _lower_ than the natural
> for the reed, it is dragged down by an additional air mass in the
> resonator.
>
>  Hopefully these distinctive features tell why inward beating reeds
> are the ones used for pipe organs.  Basically low pressure is needed,
> and high feedback (high coupling) from the resonator.  A discussion
> about this reed type only will follow.

This was most fascinating, as I am both a reed organ restorer and
professional oboist.  I came away with a completely different concept
of the underlying principals which cause the various types of reed
behavior.  (What kids call a "well, duh!" experience).  On observation,
I would have expected free reeds to exhibit a nature combining the two
types of beating reeds since the tongues relation to the frame places
it first upwind and then downwind through its full cycle.

I hope Professor Liljencrants in his next discussion can include a word
about cylindrical vs. conical resonators.  I have wondered at the "why"
behind their special characteristics and how one causes the nodes to
aggregate at one end only.

Regards,
Robert Linnstaedt