I frequently receive this question when servicing pianos. The most accurate answer is: as often as possible. However, I intend to provide a little more guidance.
The fact is that your piano begins to fall out of tune as soon as tuning is completed. This is true of all stringed instruments. Guitarists, violinists, cellists, and other stringed instrument players tune their instruments every time they play them. Ideally, a piano would be tuned nearly as frequently, but due to the time and cost involved it is not practical for most people. In many fine concert halls, the piano is tuned before every performance and often receives a touch-up tuning during intermission.
Why does a piano go out of tune? A piano produces tones when felt hammers strike the strings within the piano. These repeated impacts cause the strings to fall out of tune. Pianos are made primarily of wood and metal which are both very susceptible to humidity and temperature fluctuations. As the materials expand and contract with those fluctuations it causes additional detuning of the instrument.
So, how often should you tune your piano? Every six months is ideal with every year being the minimum recommended frequency for tuning. If a piano is not tuned regularly, it may require multiple tunings to bring it back up to pitch. If you want more information on why it is important to tune and maintain your piano, read Why tune my piano to A-440 or concert pitch? To view our tuning prices or to book your piano tuning online, please visit our services page here.