Various forms of Piano Care and Maintenance are required for it to produce the best sound. Maintenance is also important for the appearance of the piano.
Tuning
Pianos that are prized by their owners are tuned regularly, roughly once every four to six months for domestic pianos, and always just before a performance in concert halls.
This is done partly for esthetic reasons, and partly because the longer a piano is left out of tune, the more time and effort technician will need to restore it to correct pitch.
The effect of being out of tune depends on degree. When a piano is only slightly out of tune, it loses the glowing tonal quality characteristic of a freshly tuned piano, probably because strings slightly out of tune with one another have weaker sympathetic vibrations. Pianos that are more than slightly out of tune tend to be unpleasant to play and listen to, to an extent that varies with the ear of the listener.
Pianos go out of tune primarily because of changes in humidity. Tuning can be made more stable by installing special equipment to regulate humidity, inside or underneath the piano. There is no evidence that being out of tune actually harms the piano itself.
Voicing
The felt hammers of the piano tend to harden over time. They also form grooves at the points of contact with the strings. Harder hammers produce a brighter tone quality, which may ultimately become undesirable. Piano technicians can soften hammers using special tools. They also sometimes use special solvents that can harden a hammer. In either case, an important goal is uniform tone quality across the piano, since the hammers are not used with equal frequency and therefore tend to wear unevenly. The process of altering the hardness of piano hammers is called voicing.
Over time, the action of a piano tends to alter in its function, and a skilled technician can restore it to its original level of precision, in a process called regulation. Indeed, many pianos are not perfectly regulated when released from the factory, and benefit from regulation in the store or—if necessary—after purchase.
Appearance
Pianos are furniture, and in this role they benefit from cleaning and polishing, done carefully to avoid introduction of any fluids into the piano’s interior. For many piano finishes, dust removal is better done with a feather duster than a cloth, which minimizes the abrasive effect of the dust. While the wooden lid over the keys gives protection while the instrument is not in use, it does contribute to the yellowing of the white keys over time and maintaining a white appearance is greatly assisted by closing the lid only when necessary, or better still not at all.
Restoration
Pianos have a limited lifetime, usually measured in decades. However, in some decrepit pianos, the soundboard, frame, and often at least some of the action remain in good condition, and piano restorers are able to prepare very fine pianos by replacing a large fraction of its parts. These include the strings, pinblock, bridges, soundboard ribs, hammers, and many parts of the action. Restoration is generally worth doing only if the original piano was of high quality.