This is a great little device for opening up the Cutoff Frequency when using a synth, but it also works extremely well at emulating synth strings also.
Just using the Cutoff Frequency w/ a special Linear Curve allows me to use a slight amount even though my expression pedal is using it's full movement.
By using the Keytracking w/ another special Linear Curve with larger amounts, the CC2 allows me to move 2 MIDI CC's on the expression pedal simultaneously with seperate curves which does Crescendos well enough to fool the general public.
This makes a decent Synth String sound more Symphonic.