Tuning is the adjustment of the pitch of the strings and of the musical intervals between the notes. Pianos are designed to be tuned to the international pitch standard of A-440 (the A above middle C vibrates at 440 cycles per second).
The adjustment of tone is called voicing. Over time, the tone changes as the felt hammers wear. The voicing process involves working with hammer felt to adjust the piano’s dynamic range to its optimal level.
The adjustment of the keyboard and action components is called regulation. This adjustment includes evening the weight and responsiveness of the keys throughout the piano.
Of these services, tuning is the most often required, as it is essential that the piano be maintained at pitch.