Piano tuning of an acoustic piano, is the term applied to adjusting the tension on the strings, causing the instrument to make a pleasant musical sound.
A piano is strung by using a high grade steel wire called strings.
In the bass section of the instrument, these steel wires are wound by copper wire to give them greater thickness, while leaving them flexible. In the lower bass each note has one string, these are the thickest and longest. The remaining section of the bass has two strings which are somewhat shorter and thinner. The middle section of the instrument may have two strings at its lower end. The rest of the piano will usually have three strings for each note, getting thinner and shorter as you move up the piano. The very top notes only have a couple of inches for the sounding portion of the string.
There are three variables which determine the pitch of a string. These are:
- thickness of the string
- length of the string
- tension of the string.
This is where piano tuning comes in. Each of the wires or strings is attached to a square tuning pin. A tuning hammer is used to tighten or loosen the wire of the string. When you increase the tension of the string the pitch goes up, or down if you loosen it.
Piano tuning requires a very precise adjustment of the tension on each of these well over 200 strings. Where there are two and three strings each must be at the exact same pitch in each note.
A piano tuner will usually start with an A or C tuning fork near the middle of the key-board. From there music intervals, such as thirds, fourths, fifths and sixths etc. are used to establish a musical temperament. After this foundation for the tuning has been established, octaves are tuned, using other musical intervals to cross-check for accuracy.
Here is a discussion on piano tuning produced by the Piano Technicians Guild on why a piano goes out of tune and why the pitch can change on a piano.
"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.
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.
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.
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.
The preceding article is a reprint of a Technical Bulletin 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 list of Registered Techncians in your area visit our online member directory. For a copy of this or other PTG Bulletins and Pamphlets contact:
Piano Technicians Guild, Inc
4444 Forest Avenue
Kansas City, KS 66106-3750
If you would like more info about the Piano Technicians Guild or additional piano tuning or other piano information.
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