What purpose does the midi tab in Audio HQ Environment Audio serve?
What purpose does the MIDI tab in Audio HQ Environment Audio serve?
The MIDI tab in Audio HQ can be used to assign an effect to a particular midi
controller.
This has advantages for other software applications such as Cubasis as it
allows one to control the intensity of an effect in Environmental Audio
other than Reverb and Chorus from the MIDI Mixer in Cubasis.
Take for instance the drums MIDI track below. One can alter the intensity
of effects assigned to controllers 91 and 93, normally Reverb and Chorus,
by adjusting the dials Send 1 and Send 2 respectively for channel 10 in
the Midi Track Mixer. 
Returning to the image of Environmental Audio above, if one adds a new distortion
effect, one can assign it to controller 91 say and have this new effect
instead of reverb altered by the dial Send 1 in Cubasis.