Frank, it will absolutely sound different if the soundboard hasn't been glued in place.
You could glue the soundboard and playing surface in place with just a minimal amount of flexible type glue such as a Plumber's Goop. Then after 'running your sound testing', if it doesn't meet your standard, place the call in the microwave on a lower power setting for just a few seconds to bring the glue back into it's plastic range. Just a few seconds at a time. Using your striker dowel or smaller dowel rod, push the soundboard and glass top out of the call from the bottom up, through one of the exhaust holes. If you go easy and take your time, you can usually remove both without damage to either or to the pot.
You can obtain a variety or 'fine tune your pitch and tones' quite a bit by just varying the striker material, striker dowel length and the weight of the heads; without really having to do much to your pot. However, should you desire to tweak a pot without putting in back on a lathe...opening up the exhaust by drilling more holes in the bottom of the call, thereby making a lighter pot and allowing quicker exhaust will change things. Of course, not reversible....take your time -one hole at a time would be advised. Just don't go at it like your'e beating snakes and you may have some interesting findings.