Why your piano goes out of tune
A piano can go out of tune due to changes in humidity and the gradual loss of tension in its strings. Without periodic tuning, any piano will usually go flat over time. New piano strings lose tension and go out of tune more quickly. Most piano manufacturers recommend four tunings per year in the first year of a new piano, and at least two turnings per year after that. When was your piano last tuned?
The strings inside your piano push against a wooden bridge in order to transmit vibrations to the wooden sound board. Because these parts are made of wood, they are affected by changes in humidity. When the sound board and bridge swell due to higher humidity, this increases the tension of the string and makes the pitch higher. When humidity decreases, the sound board and bridge shrink, putting less pressure on the strings and making the pitch go flat. These changes in pitch differ from string to string, making the piano go out of tune.
If humidity is controlled by some means, the change in pitch is greatly reduced. One of the easiest and most effective ways for humidity control of a piano is installing the Piano Life Saver (aka Dammp-chaser) system.
Each piano string is made of high-strength, high-carbon spring steel wire that is under a high tensile force of 160-200 pounds. The constant pulling force causes the string itself to gradually lose tension in a process called “stress relaxation.” As a result, the pitch of the note goes flat over time, even though the string is continuously pulled in the same manner. During the first year of a new piano (or a newly-strung old piano), the tension of the strings drops quickly. In later years, the drop in tension slows down. This is why new pianos require more frequent tuning in the first year.
Have your piano tuned at least once a year
In addition to the two major reasons explained above, intensive playing and loose tuning pins can make a piano go out of tune more quickly. With typical use, I recommend a piano tuning at least once a year—and preferably twice a year.
The following are the recommendations by manufacturer:
Baldwin, Kawai, Yamaha, and Pearl River: Four times in the 1st year and at least twice a year after the 2nd year.
Samick, Knabe, Kohler & Campbell, Conover Cable, Bechstein, and Sohmer: 2-3 times in the 1st year and at least twice a year after the 2nd year.
Steinways & Sons, Boston, Essex: 3-4 times in a year.