Do they have some kind of veneer peeler to get the violin wood so thin? My mom was first violin in the Indianapolis Symphony about 80 years ago, and I always was amazed by how thin her violin's wood was.
The belly and the back are carved by hand from a solid block of wood and the thickness varies all around the ‘plate’ to enhance its physical ability to vibrate. Some places have to be left thicker for strength, such as where the soundpost goes - the soundpost is a round stick that is placed under the foot of the bridge on the higher frequency side and its dual purpose is to transfer vibrations to the back plate (normally hard maple) and to keep the top plate (nearly always spruce) from collapsing under the pressure exerted by the tight strings through the bridge.
Thinner plates are better acoustically as they are more responsive to amplifying the vibrations created in the strings, but too thin results in a lack of long term strength and durability, so the maker has to use best judgment to find an optimal compromise. As the plates are carved, the maker will frequently hold them between thumb and middle finger at a point known to be relatively neutral to vibrations, thumping the plate in the area where the bridge will go, and listening to the tone for both pitch and quality. When it’s “right” (a very subjective determination) the maker stops carving. Yet another element affecting strength and tone is the bass bar, a strip of wood that is glued longitudinally under the other foot of the bridge and serves as a truss to support and distribute the load caused by the strings. It can be ‘tuned’ as well by modifying its dimensions - hide glue is used for all joining as it can be softened with a bit of water and parts can be disassembled for repair or adjustment. I’m a viola player and had always been disappointed by the response of every instrument I had played to C-string vibrations, so when I was helping a luthier buddy to build me a viola, I had him ‘tune’ the bass bar to the pitch of an open C. I assume it worked because it was the best viola for lower register responsiveness and tone quality that I have ever played.
One more design element that most people have no clue about is the decorative wood inlay that runs all around near the edge of the top and back plates. It’s traditionally made from three strips of wood - maple sandwiched between ebony. It’s inlaid in a groove rabbeted into the plates about half the plate thickness deep and located above the joint where the plates are glued (with hide glue) to the sides (ribs) and it functions as sort of a hinge to accoustically decouple the plates from the ribs.
The whole assembly is a hollow sound box and the shape and volume of the interior is also important and makers are alway playing with that variable, too. The F-holes, or sound holes are there to eliminate back pressure from the compression waves that are set up in the enclosed air. People like to say that they let the sound out, but in reality they reduce dampening of the compression waves, which would also dampen the vibration of the plates. It is the compression waves generated by the plates that make the sound that people hear.
As Clem would say, “That right thar is a full shitload o’ injuneerin’!!”
Instruments can be mass produced but their sound qualities and responsiveness are invariably thick and dead.
You never change things by fighting the existing reality. To change something, build a new model that makes the old model obsolete. R. Buckminster Fuller