The plant send impulses to the midi-instruments.
The midi-signal goes to a midi-thru-box and from there to the software (reaktor), to a yamaha cs1x and a rozzbox synthesizer. The audio-signal from rozzbox is routed and modified by a korg es-1.
The device that takes the measurements is a tool from damanhur called U1.
Go to http://www.youtube.com/user/hoever303?feature=watch for more details.