!$#%&^^%&^%& ! Soundboard is a stupid word FFS. Please, please please please stop using this term to describe lightsaber electronics. Not only is it inaccurate (“soundboard” term is specifically for creating sounds ONLY), but it really gives the impression that don’t know electronics or what a microcontroller is, (aka the actual device you’d want in a custom lightsaber). A microcontroller an electronics board that handles sounds AND motion controls, LEDs, animation, and more. Arduinos are just one example of popular microcontrollers. If you only had an actual soundboard in a lightsaber, you’d be a very very sad Jedi.
(Oh, uh… what was the original question again…? No, no you can’t. All of the functionality is built into proprietary boards, and you’d have to replace all of the blade internals to accomplish new sounds.)