Starting with v1.1.7, you can use the standard MIDI volume-expression controls with Unify:

• MIDI CC#7 (“main volume”) directly controls Unify's master volume setting.
  • You will see the volume slider at the right-hand side of Unify's Master Effects layer change.
• MIDI CC#11 (“expression”) applies a scaling factor to the current master volume setting.
  • You will hear the volume change, from zero to the current setting of the master volume fader, but the fader itself will not move.

These MIDI responses are disabled by default. To enable them, go to Unify's Settings view. Near the bottom you will find a row of four check-boxes like this:

The first two checkboxes enable interpretation of MIDI CC#7 and CC#11, respectively. Note that when these boxes are checked:

1. Unify will accept and interpret CC#7 and CC#11 messages on any MIDI channel.
2. Incoming CC#7 and/or CC#11 messages will be interpreted by Unify itself, and will no longer be passed on to any hosted plug-ins.

(In a Multi-timbral setup, this may be the opposite of what is needed. Click the link for details.)

Regarding the second pair of checkboxes, see Changing patches with MIDI.