Using the Bigsby pedal as an expression pedal

[TheLonelyStomachChillsUnlessItsDrunk]

I bought the Gamechanger Bigsby pedal mainly because I wanted a "bipolar" expression pedal -- like a foot pedal equivalent of a pitchbend wheel. The Bigsby was the only thing I could find that fit the bill. It was either that or somehow jury rig something by joining two continuous sustain pedals!

So I have it assigned to a group of pitch shifting plugins in a Live session I'm working on, and like I said, its effect is bipolar, so theoretically, when I take my foot of the pedal, it should go to zero, so it's not adding or subtracting. Unfortunately I'm having a big problem getting it to snap back to zero. It's always slightly high or slightly low -- just enough to make it sound off.

So I'm hoping there's a way to create a "dead zone" in the center, when assigning linear controllers that have a bipolar effect. I'm looking at the expression pedal's MIDI data in the MIDI Monitor app, and it looks like it always snaps back to either 65 or 64. So I just need to work out a way to make it not start adding until it sends a value above, say, 66 (just to be safe), and make it not start subtracting until it goes below 63. I mean if nothing else, there's gotta be a way to do it in MaxForLive, right?