George,
I do use stabilized woods, but not exclusively. I try to make certain that the moisture content is 9% or less before I make a call from any wood. Because the entire call is handmade, down to cutting my own reeds and cork, I can control every measurement at will (I even use my personally designed jig from sugar maple). The short answer is that the inside of the barrel as well as the toneboard can and should (depending upon who you ask) be treated, depending on the wood. To elaborate: one can control the id of the barrel and the od of the insert, which means one could CA finish the entire interior of the call, should one be so inclined. Oily woods such as Cocobolo actually repel water quite well themselves and do not require a sealant. Personally, I typically use either velvit or teak oil for the inner workings, which have served me quite well, with no issues. Wood expands and contracts with changes in humidity, it is our duty as callmakers to either anticipate this and improvise, or to prevent it as best we can. Acrylics are a pretty obvious solution but, in my humble opinion, wood sounds better and more natural.
