Spanish guitar bridges evolution
As you noficed, the soundboard of the guitar is perfectly flat and of constant thickness, opposite to a violin soundboard which combines the volume given by the arching and the thickness of wood. The function of the bracing is to modify the density and the mass of this flat soundboard at specific places, to allow vibrations to express at their best, thus giving the instrument its balance, range and volume. The bridge is nof only a useful ornament for fixing the strings at the right place, but in fact the keystone of the soundboard + bracing architecture, an important and technical external element which will pull the soundboard outwards and oppose the action of the braces inwards. It will thus actively take part in the luthier's quest of good sound.