Tuning a Piano
A = 440
Early in the 1900s, musicians agreed to standardize the pitch of the note to which they tuned their instruments. They agreed to tune to an A that vibrated at a frequency of 440 cycles per second. Before that time, the A in different parts of the world (and the country) varied. Once this standard was established, piano manufacturers began designing their instruments to be tuned to this pitch as well. When a piano is properly tuned, the A above middle C is "set" to 440 cycles per second. The piano technician gets the pitch for this note from either a tuning fork or an electronic machine.
Pitch raise
If the piano is more than slightly "flat" (below 440 pitch), it will probably need a pitch raise. When tuning a piano, the technician begins by tuning all the notes in one octave of the middle of the piano to each other. This is called setting the temperament. Then the upper and lower strings are tuned. When the tension on all the strings on the piano (there are over 200 of them!) is increased enough to get a piano that is flat up to pitch, the increased pressure on the bridges and soundboard actually cause the middle notes of the piano to go flat compared to the pitch to which they were originally set. So the piano would have to be tuned again ... and probably again ... and again ... until it was "up to pitch."
To avoid this, the pitch of all the strings can be raised to slightly above where they should be, and when this pitch raise is complete, the center notes should be very close to the correct pitch. The piano can then be tuned properly. Obviously, it takes training and considerable experience to be able to raise the pitch just the right amount.
The pitch raise is, therefore, a very rough tuning which gets the tension on the strings close to what is should be, preparing the piano for a fine tuning which will stay "up to pitch." Because of the extra time involved as well as the skill (there are piano tuners who do not know how to do a pitch raise, or who will tell you the piano cannot be brought up to pitch), technicians charge extra for this service. I charge an additional $25 for a pitch raise. Generally, a tuning after a "radical" pitch raise will not be quite as stable as a tuning on a piano that was only slightly out of tune. This is one reason to have your piano tuned regularly.
Using my Verituner software, I can now do some "moderate" pitch raises in one pass.
There is a lot of debate among technicians on whether a pitch raise must be done on pianos which are flat, or whether a pitch raise is only recommended. It is true that pianos manufactured since the early 1900s were designed to be tuned to A=440. This is where they will sound the best. However, this pitch was arbitrarily decided upon. The piano will not sound "out of tune" if the A is set to some other pitch and all the other notes on the piano are properly tuned to that pitch. However, if the piano is going to be played with other instruments (for example, you are going to accompany your child who plays the flute), the piano almost certainly must be tuned up to pitch. Other instruments cannot "tune down" very far.
I recommend that pianos be tuned to the correct pitch. However, I give people the following options if their piano is flat:
Do a pitch raise (and a tuning) or ...
Bring the pitch up slightly while doing a tuning without a pitch raise, and encourage the owner to have the piano tuned again in about 6 months, at which time the pitch can be brought up a little more. Continue this until the piano is up to pitch.
As a musician myself, I believe it is very important to develop good relative pitch. This is impossible on a piano that is not in tune with itself. Therefore I believe that tuning the piano relative to itself but below pitch is preferable to not tuning it at all.
There are many people who call themselves piano tuners who do not know how to do a pitch raise, or who will say a piano cannot be tuned up to pitch. I have encountered very, very few pianos that were tunable that could not be brought up to pitch. I have successfully raised the pitch on some pianos have been extremely low (2 or three whole steps).
I do warn customers that there is always a chance with older pianos that strings may break. However, it is usually true that the strings will break in these pianos when the pitch is changed at all - not just during a pitch raise. Piano wire can become brittle after many decades, and any change in tension can cause it to break. I tell my customers that if three strings break in the middle of the piano, I will stop tuning and consult with them about the best way to procede. If I come to a piano that has already had many strings broken in the past, that piano is probably not a good candidate for a pitch raise.