Does soundbox tension affect volume and tone
Instruments- discuss specific features, luthiers, instrument problems & questions
The direction of this discussion exemplifies why Nate's original question is so hard to answer: there are a lot of variables. He started out asking if modifying the way the strings attached to the dulcimer might increase the tension of the soundboard, thus increasing volume. But the conversation moved on to the tension of the strings themselves and now how the fretboard is attached to the body of the dulcimer. The "floating" tailpiece or, as David Beed calls it, the " decoupled tailpiece " surely affects the tension of the soundboard, but more importantly, by reducing its contact with the soundboard, it frees the soundboard to vibrate more, which changes both the volume and the timber of the dulcimer. Again, that is adding another variable to the equation. Dwain and John mentioned bracing and sound posts, which add even more variables to consider
I am not a builder, and I haven't studied physics since high school, so I might be way off base here. But I wonder if the issue is not the whether tension increases or decreases volume, but where the Goldilocks sweet spot is. On guitars, too little or too much bracing will reduce the responsiveness of the instrument. On a dulcimer, I presume, too much or too little tension (or stiffness of the wood) would not produce sufficient volume. If we were to map out the relationship between tension and volume, the result might not be a straight line, but something resembling a parabolic arc.

 
 
 Cross harp, what a concept! To play straight on the harmonica, your tonic is the 4th hole, but to get those blue notes, your tonic is the 3 hole.  I still can't play like Sonny Terry, but I can manage some amateur blues and have fun.
 ) used to tell her to imagine that a delicate egg was under her hand.  The hand should be curved to protect the egg while her fingers hit the keys. I think the same principle works on the dulcimer.
  and losing touch, like 
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