Piano Strings are elastic and always stretching. Getting them to stay at a fixed point is only possible for a short period of time. Beside the elastic properties of the strings, the setting is in wood, which is also flexible and moves when humidity changes. Therefore, just like in a guitar or violin, every time it is picked up, the musician tunes before playing. Piano strings are much heavier gauge and cast iron plate helps maintain tension longer, but the minimum maintenance schedule must be followed to keep the piano alive and the wood from cracking.
For the Concert Hall: Piano Must be tuned before each concert. If there are two concerts in a day, the piano has to be fine-tuned before the second concert. Concert pianos have a shorter life cycle because the tuning pins become loose quicker from constant adjustment. Hammers and action parts become worn quicker because different users perform with all their best and heavy technique each day.
For the average home: The best time to have your piano tuned to keep tension even is about two to four times per year, depending on the location of the piano within the home and the ability to stabilize humidity and temperature throughout the year. Most pianos respond to seasonal variation in climate and when the heat turns on, the piano would go out of tune. When the summer rains come the piano may go up in pitch. For most people, we recommend to tune when the heating cycle changes. Let the cycle take effect and schedule the piano tuning after about two to three weeks when the piano acclimates