My dulcimer is built of chestnut with a rosewood overlay on the fretboard. The chestnut is not old wormy chestnut wood, but new chestnut that Don had a source for that had recently been cut down. It had survived the chestnut blight that hit in the early part of the 20th century.
You also asked the following question:
"I have a question- You are playing in dddd Galax tuning in the key of D. What do you do on that dulcimer if you want to play tunes in A or G?"
I always get confused when talking about tuning and keys and modes and all that so forgive me if I answer this in a manner that doesn't make sense!!! Please, just let me know if I am losing my mind!!
For instance, if playing "Ebeneezer" which most folks would tune their dulcimers to DGD, I do not have to retune and it sounds just fine with the DGD folks. If I am playing a tune like "Reuben" or "Hard Times" I slide the reverse capo under the two drone strings at the first fret and play away. My understanding is that one of the advantages of the Galax tuning is that you can play D and G tunes without retuning your dulcimer. In any case, I play tunes in both keys without retuning.
I am terribly sorry if this makes no sense......my biggest problem is that I tend to play the dulcimer by ear so I can't always describe what I am doing in musical terms. (With that said, I do have a solid background in music theory as far as the piano goes, but I have never bothered to try to apply it to the dulcimer....stupid....I know!!)
Perhaps if you give me the name of an A or G tune, then I could tell you how I would play it and we can figure it out together! I'm embarrassed by my inability to answer you!