Building computer-controlled Pipe Organs is very much easier than building trackers.
You don't need complex machanical parts, but only magnets which are directly linked to a
direct power interface. This power interface is linked to a PC.

FOR A COMPUTER CONTROLLED PIPE ORGAN:
The only parts you need are:
 

Item	Availability	Approx. Price	Remarks
Pump	Available by different Companies Laukhuff (DE),Kimber Allen (UK)	1000 $	same price for trackers
Regulator	Can be built with wood parts	price of wood	see description
Body	very easy with electro-magnets equipment	price of wood	Largely less expensive than for trackers
Magnets	Many magnet builder Companies Contact P. Leray	Various prices depending on  the supplyer	Less by quantities; Car magnets could also be adapted
Pipes	More difficult, mainly for little pipes	very different prices	Ancient pipes also available
Keyboards	Midi keyboards	from 200 to 400 $ each	Can be added without limitations
Hardware (Power Interface  Comnbinator)	Combinator description	Approx equal to 1-2 stops
Software	Software description	Bundled with hardware (Standard version)