The dulcimer makers in the Galax, Virgina area developed a unique style of dulcimer. You can learn more about Galax dulcimers by visiting the website of Phyllis Gaskin. Phyllis is an excellent player and a preserver of the Galax style of dulcimer playing.
One of the features common to many of these dulcimer is often referred to as a “Galax back.” The Galax back has become an option many dulcimer makers now offer on their instruments.
A Galax back is made by gluing small blocks of wood around the perimeter of the back of a dulcimer and attaching a second back to those blocks. This arrangement prevents the vibration of the back of the dulcimer from getting muted by the players lap. This can give the dulcimer some more volume and allows making the inner back thinner and more resonant.
In the photograph is a cherry dulcimer with small ebony blocks glued in place and the outer Galax back patiently waiting to be glued to them.
The ebony blocks will soon be brought flush with the sides of the dulcimer with a chisel and file. After that the second back gets glued on.
I have friend that is playing a TK O’Brien dulcimer with this type of back. I had no idea what it was called. But I would say it does increase the volume of sound.
The common thought behind the Galax back is that it prevents the back of the dulcimer getting muted by the player’s lap. Some builders just add it to their regular dulcimer design and others design the dulcimer to have a more resonant inner back. It also depends on whether you are trying to have the back resonate or reflect sound. There’s always something new to try out!