AETHERPHON, global theremin family

I have a keyboard (a K2600) that accepts both CC pedals and breath  
controller inputs.  I have done a few experiments where I have been  
able to convert Control voltages to midi-CC messages via the pedals  
however have been unable to find specs for the inputs anywhere.

I would like to send the CV signals from my Theremax and/or Epro to  
the Breath Controller or CC controller inputs -- if I can't get this  
to work I'll have to break down and purchase a CV to MIDI converter  
(such as the Paia Midi Brain).

Does anyone have specs or perhaps a schematic that allows CV outputs  
to connect to a digital keyboard such as the K2600?

Any comments/info greatly appreciated!

-- Kevin