In my experience, wormy chestnut has more often been used for the top or soundboard of the dulcimer. Less frequently it is used for the entire dulcimer. Like someone else has already said, it is frerquently used as a top on a walnut body and gives a very mellow sound, much like an all-walnut dulcimer.
I own an hourglass-shaped,walnut dulcimer with a wormy chestnut top. It was made by Clifford Glenn on September 20, 2001. Sweet sounding 3-string dulcimer. The melody rings out, while the middle and bass drones are a little more subdued. Perfect balance between melody and drones.
I also own an Echo Hollow Tennessee Music Box made by Jared Weaver. Once again a wormy chestnut top on an all-walnut body. This one has 4 strings and mechanical tuners. The larger soundbox creates a loud booming sound that tends to drowned out the melody if played on a single string, so I usually play double melody string on this one using a noter. It was made in November 2008.
Walnut and wormy chestnut are a beautiful combination of woods.