Hi Pierre ,

I don't really know, but if I read your request correctly you're asking for uneducated opinions, so: I'd expect that it's the flexibility of the wood, and in a way it's relative softness, that give the character to the sound of most strings instruments.
I would expect that materials that can withstand the tension due to only their density would sound somewhat like an empty concrete house. That, of course, begs the question: What other materials do we have that could withstand the tension due to their structure? And would they make good instruments?

                                                                  Mysha