Modern pianos are tuned to the international pitch standard of A440. This means the A above middle C should vibrate at 440 cycles per second, or 440 Hz. The 220 or so strings in a piano produce approximately 40,000 pounds of tension on the piano's frame.
As the seasons in Minnesota change, fluctuations in humidity, as well as the normal tendency for tension to decrease, cause your piano to go out of tune.
Pianos should be tuned twice a year to counteract this inherent drift in pitch. While based near Virginia, MN, we offer piano tunings throughout the Iron Range, Duluth, Hibbing, and the rest of northern Minnesota. Even if your piano is never played, it should be tuned at least once a year to prevent the possibility of other major maintenance needs.
If your piano has not been tuned for several years, it may have dropped significantly below standard pitch, and may require a "pitch raise"--a preliminary rough tuning of the entire piano, in order to stretch the strings back to proper tension and balance the tension on the soundboard and bridges of the piano.