Over time, pianoes go out of tune. It happens due to various factors such as atmospheric changes, changes in humidity or temperature, as well as some other factors. A piano can also go out of tune when moved to a different location.
The process of piano tuning requires knowledge and experience. Usually, it starts with the reference to an external tool like tuning fork to get a beginning pitch and then tunes the other notes in the “temperament” using tempered interval relationships. Once the temperament octave is finished the tuner tunes the rest of the piano, working outward from the temperament, and using octaves and other intervals to align each note with notes that have already been tuned.
