Piano tuning
There are various reasons for your piano to go out of tune and it is important to keep it on pitch by having it tuned frequently and regularly. The usual recommendation is to get it tuned twice a year, but depending on many factors, this could easily be increased to three or four times a year. Also, the more you wait between tunings, the more difficult it will be to keep it stable and on pitch. If your piano has not been tuned for a long time its global pitch will have dropped and it might be necessary to do what is called a pitch raise as pianos are designed to sound at their best when tuned at 440Hz.