is it a MUST to handle only audio, or could be also done over MIDI? Is it for the DPX?
When MIDI is also possible, then you can take a programmable Controllerbox were you can route the limited(*) Pitch-Bend Signal to a Fader/Poti.
*) "Limited" means the fader makes over the whole range only few pitch-steps,then it's similar to "fine-tune" (=no bending effect)
That's a good idea! Well, it sort of IS for the dpx, but of course this would be cool for any instrument / audio signal.
Thing is, that the presets loaded into the dpx would have to be set up with the correct parameters concerning pitch bend information, wouldn't it?