Tuning is the first point for many pianos and the most often needed service.
Why does my piano need a Tuning and/or a Pitch Raise?

Time – The string doesn’t like to be under tension, and will work to get to a neutral state. The tuning pins slow this with the friction from the pin threading and the end fibers of the pin block, but can’t halt it entirely. This becomes more obvious and dramatic with extended periods of time.

Environment–  The room has big changes in temperature or humidity. The strings press down on the sound board, this is what allows the vibrations to transfer well. However, the sound board will expand and contract with changes in temperature and humidity. These changes cause the pressure to change on the strings putting them out of tune.

How often should my piano be Tuned?

Environment – Please read above for an expansion on the environmental reasons.

Play – When the hammer hits the string this causes a slight change in pressure, that plus vibrations, allow the pin to move more easily, pressure to change in different part of the string, and knocking it out of tune. The string may take another tuning after a short period of time to settle, stretch, and equalize if has undergone a pitch raise.