If expense was not an object, sealing an air chamber that had 32 plungers (key linkages) going into it could be done easily, particularly at the air pressures generated but the human lungs, which I believe is about 1.5 to 3 psi at most. The technology exists and several methods could be used. Manufacturing costs, maintenance, and the pressure to depress a key might go up, but with some thought, these liabilities could be minimized. The first thing that comes to mind is a simple o-ring seal about the linkages. The second idea, as I mentioned a few days ago, is to transfer the movement of the key through a rubber diaphragm.