I have been making deer calls for 6 years, just started selling them last year to people. I had my hunting friends test them in a couple of states, Indiana, Kentucky and Illinoise. The wood density does not really make that big of a difference, because most of my woods are a very dense wood. The hedge, cocoblo, purpleheart are a very dense wood, that gets the sound out, the ash would be the next hardest wood, then the zebrawood, But, several guys love the zebrawood because it does make a good sound. The black Walnut does sound good, I prefer the hedge and cocobolo wood myself, but I have hunted over all the woods I have listed and and had killed deer with all the woods, went through a bunch of different types of woods before I narrowed it down to these woods. I feel these woods give a great sound.
Overall, all the woods make a great sound, I like the ones mentioned and they all sound good, just those woods are denser and have a tighter grain than the others, so it reflects the sound better. As far as loading up with moisture, there is allways moisture, but never had one stop working, year before last it was cold down here and never had a problem. But I really do not get on the call like a duck calls, couple of grunts every 5 min. seem to work well for me.
Feel free to ask more questions.