In the San Francisco Bay Area
Most in-home pianos that receive light to medium use can hold a tuning adequately for about a year, once the piano is stable.
If the piano is exposed to frequent changes in climate, such as along the coast, or is exposed to direct heat or sunlight, such as an outside wall or a sunny window, the piano might need to be tuned more frequently.
New or restrung pianos need more frequent tunings before the piano’s pitch is stable enough to tune only once a year.
Pianos that receive heavy use, such as teaching pianos and school pianos require more frequent tuning on a regular basis.
For more information, including some piano manufacturers’ recommendations, see the Piano Technician’s Guild article about how frequently to tune a piano.
Pianos Not Serviced in Over a Year
Many pianos that have not been tuned for a year or more have lost some of their 18 tons of structural tension and require what is known as a pitch raise. When a pitch raise is performed, the piano strings are retensioned and then tuned. I do this in one sitting and take slightly longer than a standard tuning. The cost for a pitch raise is moderately higher than for a standard tuning.
It is important for a piano to be tuned to standard pitch. When a piano is below pitch, its value as an ear-training tool in piano instruction is compromised. In addition, a piano that is below pitch or out of tune is undesirable when playing with other instruments or singers.