The pitch of a piano refers to its relative sharpness or flatness. In technical terms, the pitch of any given note can be measured in hertz, which is vibrations per second.
The very lowest note on (the left hand side of) a piano usually vibrates around 27 1/2 times per second while the highest (on the right side) exceeds 4100 times per second.
Standard pitch was adopted around 1925 when all musicians agreed that the "A" above middle "C" should vibrate at 440 times per second. When a piano is tuned to standard or concert
pitch, it is said to be tuned to A440. That note is usually set to a tuning fork or an electronic device and the rest of the piano tuning is based upon that note.
Seasonal climates changes will affect the pitch of a piano as well as the tuning.
Why should your piano be tuned to standard pitch?
Actually it is up to you if this matters to you - the piano doesn't really care and it will sound fine if it is tuned where it stands (which may be at standard pitch anyway).
Here are reasons why you would want it tuned to standard pitch:
You want to play along with CDs. Practically all CDs recorded today are recorded at standard pitch.
Other musicians come over with their instruments to play along with the piano. Many musical instruments do not have the ability to tune to very far away from standard pitch.
You have a serious voice or piano student in the household. Voice students need to train their voices with the piano. When they are singing an "A" they need to hear a proper "A". If the "A" on the piano sounds like a standard "A" flat, they will be surprised when they perform with standard tuned instruments and wonder why the "A" was so hard to reach when they could reach it with their home piano. A serious piano student is one who is playing through more advanced music such as Beethoven or Liszt Sonatas.
Pianos are generally designed to be tuned at standard pitch. A very flat piano will also have flattened tone.
It should be pointed out that manufacturers generally design their pianos to be tuned at standard pitch for the best tone. Also: Having a pitch correction performed is a waste of money if you are not committed to tuning the piano at least twice a year because the pitch is likely to drift again if allowed to move along unchecked by regular tuning.
Some older pianos with tuning stability issues may not be able to hold a tune at standard pitch and may need to be tuned somewhat flat from A440.
