The reverb can be changed either through the live control knobs or the function menu. The live control knobs will affect the main and dual voice at the same time, whereas when you go into the function menu, you can adjust the levels of the main voice and dual voice individually (you can also adjust the reverb level of the split voice, as well). This would be good if you want to have a dual and/or split voice that contains some reverb, but want to zero-out the reverb on the main voice -- assuming that you are selecting the Live Piano as the main voice.
Another option -- you can just use the function menu to go to the overall reverb type, and select to turn off the reverb altogether, but of course, this will turn off the reverb for all three voices -- main, dual, and split.
With all of that said, if the actual sample/digital recording of the Live Piano voice has some "baked in" reverb, then you cannot get rid of this. It's just part of the sound. But if all of the reverb for the Live Piano sound is supplied by the reverb effect, then the above suggestions will remove the reverb. If you want to the be able to access this sound easily in the future, without having to adjust all of these reverb parameters each time you want to use the sound, then you can save it in a registration.
