In 000124 MMDigest, Jim Cook wrote:

> ... the technology certainly exists to have pulse proportional
> control over the air valves, though the cost might be a bit high.

Actually, a proportional system for pipe organs is available from
Syncordia International Inc.,  http://www.syncordia-intl.com/spropa.htm
It uses Hall-effect sensors on the keys, and proportional magnets on
the wind chests; it can even emulate the touch of tracker keyboards by
additional magnets on the keys.  The bad news is its price: according
to my information (second-hand information, however), the cost is about
250 US$ for each single sensor-magnet couple, including the electronics
in the middle.

It doesn't solve all problems, however.  If the console is placed at
some distance from the pipework, the organist will perceive the sound
with some not-negligible delay, due to the speed of sound, and that
could be an obstacle for a fine performance.  It is a long debated
problem.

Some time ago an organist told me that he overcame the problem of
distance by using a microphone placed near the pipes, linked to
earphones at the console.  Even with a low volume, it gave him the
perception of the sound of pipes immediately.  It was impractical
when he played with a choir or other instruments.  I prefer tracker
organs...

Regards

Leonardo Perretti