TECHNICAL BULLETIN #1
PITCH RAISING
(revised 8/26/94)
© 1992 & 1994 The Piano Technicians Guild, Inc.
Why does a piano's pitch change?
Won't tuning restore my piano's pitch to A-440?
How far from standard pitch must a piano be before a
pitch raise is necessary?
How long does a pitch raise take?
Your piano is designed to sound its best when tuned to A-440 (A above
middle C vibrates at 440 cycles per second), 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.
Why does a piano's pitch change?
Piano strings change pitch for two primary reasons: the initial stretching
and settling of strings when the piano is new, and soundboard movement
due to humidity variation. In the case of new pianos, the pitch drops quickly
for the first couple of years as the new strings stretch and wood parts
settle. It's very important to maintain any new piano at the proper pitch
during this period, so the string tension and piano structure can reach
a stable equilibrium. (Most piano manufacturers recommend three to four
tunings the first year, and at least two per year after that.)
Aside from this initial settling, climate change is the main cause of
pitch change. That's because the piano's main acoustical structure -- the
soundboard -- is made of wood. While wooden soundboards produce a wonderful
sound, they also react constantly to climate changes. As the relative humidity
goes up, the soundboard swells, increasing its crowned shape and stretching
the piano's strings to a higher pitch. Then during dry times the soundboard
flattens out, lowering tension on the strings and causing the pitch to
drop. The drop in the dry season tends to exceed the rise during humid
times, so the net result is a drop in pitch each year that the piano isn't
serviced.
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Won't tuning restore my piano's pitch to A- 440?
If a piano has gone without tuning for an extended period, its pitch
may have dropped far below A- 440. This means that each of its approximately
220 strings needs to be tightened considerably, adding tremendous additional
tension to the piano's structure. The problem is that as each string is
tightened, the additional load causes the pitch of previously adjusted
strings to change. Thus it is impossible to make a substantial change in
pitch and end up with a fine, accurate tuning in one step. Instead, a process
called "pitch raising" must first be done, in which all strings are raised
to their correct average tension levels. (Likewise, when a piano's pitch
is higher than standard, a pitch lowering procedure must be done to reduce
string tensions to approximately correct levels.) Only then can the piano
be accurately tuned. In other words, accurate tuning is only possible when
all strings are so close to their proper tension that only small further
changes are needed during tuning. These small changes then do not disturb
the tuning of other strings.
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How far from standard pitch must a piano be before a
pitch raise is necessary?
Just when a pitch raise or lowering is necessary depends upon how
accurate the final tuning must be, and the size and quality of the piano.
Any net change in a piano's string tension during tuning will distort the
final result and reduce stability. Realistically, a pitch difference of
a few percent can usually be accommodated successfully during tuning. For
average situations, when a piano's pitch is noticeably different from that
of other standard pitched instruments, a pitch correction procedure is
necessary before tuning. Whenever exact pitch level is critical, such as
in concert or recording instruments, any pitch deviation must be corrected
before tuning.
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How long does a pitch raise take?
A pitch raise is essentially a special tuning procedure designed
to leave the piano approximately in tune. For moderate pitch corrections
the procedure takes about the same time as a tuning, or less. Extreme pitch
changes may require two separate pitch adjustments.
The pitch adjustment and subsequent tuning may be done in one
visit, or the tuning may be scheduled for a short time later depending
upon how far the pitch had to be changed. In general, the longer a piano
has gone without regular service, the more tunings will be required to
reestablish tuning stability.
Like your car, your piano is a major investment which deserves
regular servicing to keep it working well and preserve its value. Most
importantly, the well-maintained piano sounds better, plays better, and
gives you and your family a wealth of musical pleasure.
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The preceding article is a reprint of Technical Bulletin #1 published
by the Piano Technicians Guild, Inc. It is provided on the Internet as
a service to piano owners.
Piano Technicians Guild is an international organization of piano technicians.
Registered Piano Technicians (RPTs) are those members of PTG who have passed
a series of examinations on the maintenance, repair, and tuning of pianos.
For a copy of this or other PTG Bulletins and Pamphlets, or a list of
RPT members in your area, contact Piano Technicians Guild, Inc., 3930 Washington,
Kansas City, MO, 64111-2963. Phone: (816) 753-7747 FAX: (816) 531-0070
E-mail ptg@ptg.org
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