Robbie wrote [ 000424 MMD, commenting on "Reed Voicing in Organ Pipes,
by John Nolte ] :

>[ If a metal reed were electrically isolated from the metal shallot,
>[ a capacitance meter circuit would provide an electric signal which
>[ varies with the motion of the reed.  Modern conductive plastic
>[ material could be placed on the face of the shallot to yield a
>[ transducer whose conductance is in proportion to the contact area.

This is the same principle used in the Wurlitzer Orgatron.  This
instrument, circa 1950, is essentially an amplified reed organ.  The
reed is one side of an air-gap capacitor, and an adjustable screw
placed above the reed provides the other.  No plastic needed :-)

In other respects, the Orgatron is set up as a unified direct electric
organ.  Some of the stop tabs select combinations of reeds from the two
ranks to simulate various instruments - horn, oboe, etc.

The Orgatron is an interesting step in the evolution of "electronic"
musical instruments.

Mike Blackwell