The piano Soundboard is made of strips of spruce wood glued together.
Soundboards are usually built with a slight curvature called “Crown” which like a magnifying glass, magnifies the sound. This is actually the “speaker” of the piano. It is glued along the perimeter to the rim of the piano and acts as a diaphragm
Strips of wood called “Ribs” are glued to the back of the Soundboard so as to maintain its curvature. Sometimes in old pianos, ribs become unglued which result in a buzzing sound when the instrument is been played. Using special tools and techniques, loosened ribs can be re-glued.
Building a new Soundboard is a very technical procedure. Below, are some pictures of some of the processes.