Selmer have a pitch shift in its sound. And the Ovation Guitar and the Turkish Long necked Lute Tanbur have pitch shift - it has 112 cms long strings -
Selmer and Tanbur have a distorted soundboards by weight of bridges and they shift pitch. Their unique soundboard flexure makes nonlinear shift.
Ovation has it with glass reinforced polyester soundboard with covered with veneer. The combination of each glass fiber direction , Ovation have nonlinear shift by distorted material not by the pressure of the bridge on the soundboard.
Ovation have the most pitch shift with the intense nonlinearity of fibers and the intense modal party at the higher pitch sounds. It has a high end heavy sound signuture. It has squak.
But for defense of Ovation , coast guard tried to imitate the flex and strenght of atlantic turtles and they wanted to make propeller hitting experiments for turtles. Closest material was polyester wetted glass fiber.
You know the fight for turtle picks...
Now I want to make a maccaferri and I dont have any tool and wood. I want to glass reinforced plastic one but glass fibers does squak.
I read that the fiber closest to wood is polyethylene fiber. I will butcher the guitar even more and it will have hand layed soundboard and hand layed neck , not anymore . Sides and back requires extensive work and jigs and if I would have hundreds of dollars for laser cut, ultra expensive thick acrylic , I would buy a 650 dollars maccaferri copy.