The Soundboard, made typically of spruce, acts as an acoustic amplifier. The Bridge works as a transducer, transferring the vibrations of the strings to the soundboard. The rim provides structural integrity, holding all the parts of the piano belly together, in addition to being a major part of the aesthetic cabinetry. The pinblock holds the pins, which act as sophisticated screws where the strings are wound. Turning the pins with a tuning hammer tightens or loosens the strings, which in turn affects the pitch of the string vibrations.
For the best sound production, the soundboard needs to be constantly in a state of tension. To achieve this, the soundboard is designed with a curve supported by ribs underneath. The crown of the soundboard is where the bridges are placed for maximum sound production and amplification.
The pinblock is made of multiple laminations (layers) of hard woods (like quarter-sawn maple) to ensure that the pins are gripped securely with contrasting grain orientations of the wood.
The piano rim is actually composed of outer and inner parts. The outer rim is the visible cabinet, while the inner rim acts like a shelf to hold and support the soundboard and pinblock. The rim is composed of multiple layers of wood laminates which are bent and steam pressured into the shape of the piano.