Abstract: A plate assembly as herein disclosed can be constructed to be used in place of the plate assembly in any piano. It is constructed primarily of composite material and replaces the conventional cast iron plate or plate assembly. The assembly has better shape and dimensional stability under the influences of time, temperature variation and moisture, and is lighter weight and lower cost. These features allow use of a lighter weight piano frame. The net results are that a piano having optimum performance is more readily transported, its manufacturing and maintenance costs are less and the effects of time, temperature variation and moisture are minimal. The plate structure comprises specially designed and joined composite material elements, arranged to take best advantages of the characteristics of composite materials applied to serve the functional/structural purposes of piano plates.