When a piano has not been tuned is some time, usually 2 years or more, the piano will likely need something called a pitch raise or pitch correction before the final fine tuning. A pitch raise tuning is a rough “pre-tensioning” of the piano strings and “pre-pressurization” of the sounding board to create a more stable final tuning. This is necessary when the piano has dropped significantly in pitch. The reason we do this is because the act of pulling the strings up to pitch puts enormous amounts of tension on the piano, which can alter the previously tuned strings.
For the sake of efficiency, I use an electronic tuning device to assist with this process. The tuning device will take the required measurements and calculate the proper amount of “over-pull” tension necessary to allow the piano to be finely tuned without any further drop in the pitch of the strings. The precise calculations also help to prevent string breakage by limiting the amount of “over-pull” to an acceptable range. Doing so, however, may require another pass through the piano’s tuning pins. This is done however many times it takes to safely bring the piano up to the pitch it was designed to hold, usually A=440Hz.