The Pitch Bend range on the Model D can be changed within the Synth Tool application. Open up the application with your Model D connected to your computer via USB lead and switched on. In the first page (General), you’ll see two options for Pitch Bend: Mode and Semitones.
If the Mode is set to ‘Fixed,’ you will not be able to change the Pitch Bend range. If you change this to ‘Settable,’ the option below will then allow you to change the number of semitones of pitch bend. When you exit the application or power cycle the device, the mode will change back to ‘Fixed,’ but the range will stay as you set it.