Keeping your piano tuned on a regular basis, (twice a year) is the most important thing you can do to help maintain the instrument's value. Changes in temperature and humidity causes changes to the tuning of the piano. A piano's sounding board is made of wood, and with seasonal changes in the weather, this wood contracts and expands. This causes tension and stretching on the strings which causes the overall tune of the piano to change. Not only will regular tunings keep the value up on your piano but will definitely make the sound much more pleasing to the player and listener!