The action of a piano is virtually an extension of the performers’ fingers. Actions are mainly made by specialist firms, but some piano manufacturers make their own. Creation of an action is a complicated part of piano making and each complete action, including hammer and keys, involves about 5,000 operations.
Various methods of manufacture are used, the classic method begins with the hammer heads, which are covered with a special felt which has been cut into long wedge shares. Each strip of felt is placed on a caul and covered with a thinner, red underfelt. Hammer woods, already moulded and cut, are glued and placed in a jig posed above the felt which is then forced down into the felt with a pressure of eight tons and left for some hours.
The felt is trimmed, and the woodwork cleaned and each head guillotined and the two ends of felt pinned or stapled. A hole is bored in every head, and the hammer shank glued into position. There are about 20 different wooden components for each action section.
Wood for the keyboard has to be panelled to ensure that the grain runs in the correct direction, is cut into the right length, grooved and shaped. The key covering is then laid in position with a suitable adhesive. Ivory and ebony are used today for the finest concert pianos and the most expensive uprights. For most pianos, the covering of the white notes is an acrylic plastic sheet. The exact position of each note is marked on the plastic and each key is numbered. The board is then cut into individual keys which are put onto a frame, regulated and spaced before the black notes are attached. The latter are made from another modern plastic.