The pitch standard for tuning pianos is to tune the A above middle C to a frequency of 440, known as A440. There are many reasons the overall pitch of the piano can deviate from that standard. A few of those reasons are:
- New strings – whether on a new or restrung piano
- Change in the relative humidity in the piano’s environment
- Neglecting to have the piano tuned for more than a few years
- Direct sunlight
When the pitch is more than a certain amount sharp or (most commonly) flat from A440, then two passes through the tuning are required. The first pass is considered a pitch correction – the purpose of which is to bring all the notes to their proper pitch relative to A440. The second pass is considered a fine tuning – the purpose of which is to establish all the notes in their proper relationship and to solidify the tuning.
Performing a pitch correction usually necessitates an additional charge to the base tuning fee, since more time and effort are put into the process of restoring your piano to it’s best sound.