Tuning involves adjusting the tension on all the strings in the piano, so that they vibrate at the appropriate frequencies. There are more than 200 strings in a piano, and the combined tension of all the strings ranges from 18 to 20 tons. Special tools are needed, and special skills are required. The tuning process begins by setting the A above middle C to 440hz, the international pitch standard. Then, the other notes are tuned in relation to the A, so that all the notes are in proper harmony with one another.
Regulation is the adjustment of all the moving parts of the keys and action, so that the action of the piano functions at peak efficiency, control, and power. In a complete regulation, thousands of adjustments must be made, some down to a tolerance of one thousandth of an inch.
Repair of the piano is needed when parts are broken, or worn to the point they cannot properly perform their function. Sometimes this involves replacing a broken part with a new part. At other times, the broken part can be repaired by gluing the broken pieces back together, or replacing worn felts or leathers.
When considering rebuilding a piano, either partial or complete, it involves major replacement of worn parts and renewing the piano to new, or like new, condition. Every part of the piano is subject to replacement or detailed reconditioning. Almost always the soundboard and the cast iron plate are cleaned and refinished. The case is usually repaired and refinished. New strings and tuning pins are installed, and the keys, action, and back action, trapwork, and pedal assemblies are renovated. Complete action regulation, shop tunings, and voicing finish the job. This type of work takes months in the shop, but the piano is restored back to excellent appearance and performance.
Voicing puts the finishing touch on the tone of the piano. It mostly has to do with conditioning the felt of the hammers, which generate the sound of the piano by striking the strings. However, preliminary work must be done to level the strings and seat them at their bearing points. Then, hammers are mated to their strings so that each hammer strikes all its strings simultaneously, and at the proper point and proper angle. After this, work with the hammer felt can commence, using needles and sometimes a judicious application of lacquer or other hardening agents.