What is a Pitch Adjustment, or Pitch Raise?
While a piano only has 88 notes, there are roughly 225 to 250 strings in a piano. Those strings exert in the neighborhood of 10 tons of tension across the soundboard and plate. Now, bear with me for a moment and imagine high top shoes. By the time you finish lacing them up the first time, the bottoms are loose again. With me so far? Good! Because the same thing happens in a piano. If the tuning is too far out, and a single pass tuning is attempted, all that tension will shift around and where the tuning was started will no longer be in tune by the time the tuning has been completed.
A Pitch Adjustment is a very quick tuning that, while it does not leave the piano in tune, does bring all the strings up to tension. That done, now a second pass "Fine" tuning can be accomplished, leaving the piano in tune when completed.
A pitch adjustment should be expected if your piano is more than three or four cycles per second, or Hertz, away from the standard of A440 Hz. Pitch can sometimes change this much in as little as a couple of years.
Your piano is designed to sound its best when tuned to A440 (The A above middle C vibrates at 440 cycles per second, or Hertz.), the international pitch standard. At this pitch, power and tonal range are optimum and your piano will match the pitch of other instruments. When your piano varies from A-440, pitch adjustments are required to bring it back to standard. By always maintaining your piano at standard pitch, you create long-term tuning stability because the strings and structure stay in equilibrium. You also ensure proper ear training because you always hear your music in the correct key.