Tony Harminc asked about tactile feedback from keyboards.  There are
a couple of techniques for giving "tracker touch" to electric keyboards.
One method is to have an over-balanced spring for each key arranged
such that as the key is depressed the spring pivots and suddenly offers
no more resistance.  The result is that the key pressure is high
until the pivot point and then it is low, simulating the pluck of a
large pallet valve on a slider windchest.  The second method achieves
the same basic effect by mounting steel plates to the top of each key
and placing a long magentized steel bar across the tops of the keys.
(This assumes keys with rear pivots.)  When the key is at rest, the
magnet attracts the plates, giving extra force holding the key up.  When
the organist pushes the key, it moves away from the magnet which then
ceases to attract the key. The result is a similar sudden drop in key
pressure.
 
In principle, one could use electro magnets in place of the magnetized
bar and could control the magnet force to vary the key touch.  Such
a system might be too bulky and power hungry for practical use.
 
A tip of the old hat to you, Tony!  (He and I were both VM systems
programmers in a previous life.)  Larry Chace ([log in to unmask])