What the hold button does is pretty simple. As noted it is for the touchstrip on the command station modules. Think of it as a pitch wheel. when you move the wheel its spring causes the value to jump back to zero when you're no longer touching it. same thing with the touch strip. if you press it it goes to a value, when you remove your finger it goes back to zero. having 'knob hold' on makes the touch strip retain and stay on whatever value was last pressed.. so you don't need to keep your finger constantly held down on it.
i've never used the feature with the P2500 (i have an XL7) but by default the touchstrip controls pitch wheel modulation in most patches so I assume that is what is happening with the P2500 as well.
i've never used the feature with the P2500 (i have an XL7) but by default the touchstrip controls pitch wheel modulation in most patches so I assume that is what is happening with the P2500 as well.