Why does a piano go out of Tune?
A piano goes out of tune because of humidity, time and use.
The most significant cause of a piano going out of tune is humidity. In high humidity the wood in the piano expands and in dry weather the wood shrinks. Much like a guitar, the strings in a piano rest on a bridge that is mounted on a soundboard. Therefore, a change in the humidity alters the pressure on the strings causing the pitch of the piano to be higher in damp months and lower in dry months. You may even notice a change in your pianoís sound when the furnace starts running in the winter and the humidity drops in your house.
If your piano is tuned regularly and the humidity doesnít change dramatically during the year it will stay in fair tune. It is best to have your piano serviced at the same time during the year to insure that the relative humidity in the wood in the piano is consistent each time it is tuned. The good news is that weather conditions (fairly consistent humidity levels) here in the Lower Mainland are actually good for pianos.
Time and physics cause a piano to go out of tune. A small apartment piano has about 12 tons of pressure across the back and a concert grand can hold up to 23 tons of pressure. All of this pressure over time causes the tension on the strings to lessen and go out of tune. That is why a piano that is not tuned for a few years may need a Pitch Correction.
Playing the piano does not affect the tune of the piano significantly if the piano is tuned correctly. A piano is made to be played loudly. Tuning a piano correctly, a technician sets both the pins and the strings to make sure that they donít slip. You may notice a technician playing a note repeatedly with sharp hard blows. This is to make sure that there is no slippage.