Most Manufacturers recommend tuning pianos 3 to 4 times a year for optimum performance. I recommend tuning twice a year for pianos that are played on a consistent basis. Pianos that are not being played should be tuned once a year to maintain the integrity of the instrument.
When a piano is not being used on a regular schedule, the music wire starts to go flat, or in other words, drops in pitch. A pitch raise is the tightening of the music wire to the designed pitch of the piano. Adjusting the pitch adds several thousand pounds more pressure to the piano's structure and causes the music wire to move through its bearing points. After the pitch raise is completed, the piano will need seven to ten days to acclimate to the new tension before it will accept a good, solid tuning.
Regulation is the timing of all the parts in a piano action There are 8 steps to regulate each piano key and it typically takes ten hours to properly adjust all 88 keys. In the beginning, a new piano action will need minor regulation during its first year of use and a full regulation in three to five years. Pianos in universities, colleges, and schools will need regulation more often because of extensive playing.
Aural tuning refers to a piano that is fined tuned by the human ear. Using a tuning fork (A-440 CPS cycles per second) to start the process, the piano craftsman builds a temperament or musical scale using fourths and fifths and progressive thirds to fine tune an octave in the middle of the piano. He then tunes the rest of the piano to the carefully crafted temperament. All pianos tune differently and it takes years of experience to finesse the best temperament possible for each instrument.
Voicing is the blending of all the notes on a piano. The piano craftsman needles and files the piano hammers to voice up or down the volume of the piano. This process also adjusts the tone quality. Each instrument has a characteristic sound of its own and the piano craftsman works toward the best tonal combination