Please disregard my poor playing here.. 
this is a bad demo of 3 levles of expression possible with Akai Force as a Midi Instrument (I am using Audio Modeling Violin here)

Level 1: Just playing the pads with no aftertouch. not much expression (the factory default way)

 Level2 : Using Pad Aftertouch (Pressure) for Vibrato amount.  Please Note: My Force has my Aftertouch tweak Mod Enabled (Mockba Mod). which gives me bit better control over it (delay and deadzone).

Level 3: CC:11 (Expression) also Mapped to Cross Fader . So I play notes with left hand and control expression with Right.. (yu could also use a usb breath controller or a midi expression pedal.... but I am doing all from the force itself..

Akai Force - Expression - Demo - Proof of Concept

atalwar