How Is a Piano Tuned? Is It Difficult?
To the uninitiated, tuning a piano may seem a simple, straightforward procedure, but it isn’t. The process is complicated by the sheer number of strings and tuning pins (more than 200 of each, the exact number varying with the model), by the high tension under which the strings are stretched, by the tightness with which the tuning pins are anchored in the pinblock, and by the friction points over which the taut strings must slide as they’re being tuned. All of these factors are obstacles not only to tuning, but also to creating a tuning that will be stable for a reasonable length of time, given the piano’s use and environment.
Tuning is also potentially made more difficult by the design element of modern pianos known as loop stringing. In loop stringing, each length of steel music wire in the treble actually forms two strings, which are separated by a sharp bend in the wire where the strings are anchored to the piano’s castiron frame. Sometimes these two strings sound the same note and are tuned to the same pitch. Other times, they are parts of adjacent notes, with one half of the wire tuned a half step higher or lower than the other half, the two halves necessarily held at distinctly different tensions. Because all parts of a single wire have a tendency to seek the same tension, loop stringing is a more challenging environment in which to learn how to create a stable tuning.
In addition to physical obstacles, there are acoustical obstacles to tuning. A paradox common to all fixed-pitch instruments, first discovered by the ancient Greeks, is that it’s impossible for all the intervals — thirds, fourths, fifths, sixths, etc. — within a perfect octave to themselves be perfect. This problem is dealt with by slightly expanding or contracting — tempering — each of these intervals so that, together, they will add up to a perfect octave. The tuner creates a temperament — a single octave of 13 notes at the center of the keyboard in which every note is tuned in its correctly tempered relationships to all other notes in that octave — and then copies those relationships to all remaining sections of the keyboard by tuning each note to be a perfect octave (or octaves) above or below the corresponding note in the temperament octave.
But even the phrase perfect octave is a bit of a misnomer. Vibrating strings give off harmonics — fainter tones whose frequencies are in a specific mathematical relationship to that of the fundamental, or principal frequency at which the string is vibrating. For a piano to sound right, the tuner must tune each string so that its harmonic and fundamental frequencies are all in tune with those of the other strings. Due to the stiffness of steel strings, the frequencies of their harmonics are somewhat higher than the theoretical ideal, a property called inharmonicity. In addition, the human ear tends to hear the higher pitches as a little flatter than they actually are. To compensate for these effects, the tuner must tune (stretch) the octaves a bit sharper in the treble and a bit flatter in the bass than would be the case were the octaves actually perfect. How much sharper or flatter is both an art and a science, which is one of the reasons why some astute musicians may prefer one tuner over another.
To tune each note, and then to confirm its accuracy, the tuner performs certain listening tests. These tests require listening to faint, regularly undulating interference patterns in the soundwave, called beats, that occur when two notes that form an interval are played together, and harmonics of the two notes are at almost but not quite the same frequency. The tuner tunes one of the notes so that the beats are either eliminated (beatless) or occur at a certain precise rate of speed, depending on the particular test and the interval being tested. In addition, most notes on a piano are sounded by sets of two or three strings each, called unisons; to sound in tune, every string in a unison must be tuned at precisely the same pitch — that is, they must be beatless relative to each other.
When you combine tuning’s physical and acoustical obstacles, you can see why it takes years of training and practice to become an accomplished piano tuner.
What Tuning Does Not Include
Tuners often arrive at a service call to find a piano with sticking keys, hanging dampers, and/or broken parts. However, tuning involves only correcting the pitches of the strings. It does not cover cleaning, adjustment, or repairs to the mechanical, structural, or cosmetic parts of the piano, or voicing (tone adjustment). The tuner and client should discuss these other needs so that both clearly understand the work to be done and how much it will cost. That said, if a piano problem is caused by something accidentally dropped inside the piano, such as a pencil or hair ornament, and it can be removed with no more than a few minutes’ work, the tuner will often include that service in the tuning fee.
When contacting a tuner, be sure to let him or her know the piano’s brand and model, whether it is a vertical or a grand, when it was last tuned, and any repairs or adjustments you believe need to be made. This will allow the tuner to allot sufficient time, and to be prepared with the proper tools and materials for the job.
How Often Should a Piano Be Tuned?
This is the question most frequently asked by customers. The answer depends, first, on the piano’s use. In the most critical situations, such as in a recording studio, where the accuracy of the tuning will live in perpetuity in a recording, the answer is probably every day, or even several times a day. In concert halls and other performance situations, the piano is tuned before every rehearsal and every performance, and sometimes the tuning is even touched up at intermission.
For a piano used in the typical home, tuners usually state the recommendation in terms of so many tunings per year. Because a piano is always going out of tune, beginning as soon as the tuner has finished the job, the frequency of tuning will depend on the tolerance of the pianist to changes in pitch, the piano owner’s budget, the ability of that piano to hold its tuning, the consistency of the temperature and humidity in the room the piano is kept in, and in how skillful the tuner is in creating stable tunings. For most home pianos, the owner will be satisfied if the piano is tuned two or three times a year. For professional use or fussier owners, four to six tunings a year, or even more, may be appropriate.
Why Won’t My Piano Hold Its Tune?
First, we consider the physical condition of the piano, something of which many owners will not be aware — the instrument could be faulty due to age and wear. Various conditions, some described in terms of “cracked” parts and often confused by customers, may or may not be affecting the ability of the piano to hold its tune:
Pinblock — The pinblock is a plank of laminated hardwood, located beneath the cast-iron plate at the front of a grand or at the top of a vertical, into which holes are drilled for the tuning pins, and into which the pins are driven and tightly held. Over time, these holes can expand slightly from wear, age, and dryness, causing the tuning pins to loosen and no longer be able to hold the strings at their correct tensions. Cracks can also appear around the holes or between laminations (thus the term cracked pinblock). A worn or cracked pinblock is the most common structural cause of a piano’s inability to hold a tune.
Plate — The cast-iron plate or frame, along with the piano’s wooden case, is the primary structural support for the tension of the strings. On rare occasions, the plate will crack, usually rendering the piano untunable, and possibly unrepairable. This can happen due to a design flaw or a flaw in the casting, or due to extreme mishandling of the instrument during moving, such as dropping the piano from a height. Cracked plates are very rare; most technicians will see only a few in an entire career.
Soundboard — The soundboard is a thin wooden board, usually of spruce, that is partly covered by the cast-iron plate. The soundboard is made to resonate by the vibrating strings, thus amplifying their sound and transmitting it to our ears. Just about everyone has heard of a cracked soundboard. However, soundboard cracks have no effect on a piano’s ability to hold its tune.
Bridges — Bridges are strips of hardwood, glued to the soundboard, that transmit the strings’ vibrations to the soundboard. The strings are stretched over the top of the bridges and bear against them, held in place by bridge pins. Age, dryness, and the pressure of the strings against the bridge pins can, over time, cause cracks to form around the pins, which then loosen. Except in extreme cases in which a bridge is virtually falling apart, the principal effect of loose bridge pins is not on the ability of the piano to hold its tune. Rather, loose bridge pins provide insecure termination points for the vibrating strings, causing tonal irregularities called false beats that, when excessive, make the affected strings sound out of tune even when they’ve been tuned as well as possible.
Strings — Metal fatigue, rust, corrosion, pitting, and any history of liquid spilled into a piano can cause false beats and other irregularities, making tuning more difficult and less accurate. Due to the effects of metal fatigue, concert instruments may require restringing in as few as 10 years. Pianos in the home may benefit from restringing after about 25 years of use, though few receive that treatment.
Daily and, especially, seasonal variations in humidity are the most common cause of pianos without structural flaws going out of tune. The soundboard swells and shrinks slightly with changes in humidity, altering the tension on the strings. Wide swings of humidity can keep a piano’s pitch in a constant state of flux, forcing the tuner to radically change the pitch with each tuning. The further out of tune the piano gets between tunings, the less stable its tuning will be when it does get tuned. When making a large pitch correction, the tuner may tell the customer that the piano is too flat or too sharp for a stable tuning to be done in a single session, and that after getting the tuning close to accurate, he or she will have to return in a few weeks to retune the piano. If the customer fails to have the piano tuned regularly, it will seem to be always out of tune. I have many customers who, in order to keep their pianos as close to pitch as possible, have them tuned once a month. It’s not uncommon for pianos kept in the faculty and practice studios of conservatories to be tuned two or three times a month; concert pianos, even when not in use, are usually tuned once a week just to keep them close to pitch. Tuning stability can be greatly increased by use of a humidity-control system — for the entire home, for just the piano room, or inside the piano itself.
Counterintuitively, frequent service is particularly important with new pianos. Brand-new instruments can be very unstable as their new strings and soundboard continue to settle, and in their first year usually must be tuned four to six times. Most dealers will tune a new piano before delivery, and once or twice after delivery, often at no additional cost to the customer. Depending on how many times it was tuned on the dealer’s floor, and before that in the factory, this may or may not be enough to stabilize the piano so that the frequency of tuning can return to whatever the customer considers normal. Failure to ensure that the recommended post-sale service is actually done can substantially lengthen a new piano’s break-in period and make its tuning seem unstable.
A piano’s tunability is also a factor of its quality and price — when offering a piano at a particular price point, manufacturers take into account the sophistication and expectations of prospective purchasers. More expensive pianos can be tuned more accurately, and, given equivalent conditions of use, will usually hold a tune better than less expensive ones because of their superior designs, better materials, more robust construction, better workmanship, and more extensive preparation in the factory. Due to globalization and the increasing computerization of manufacturing, these differences are less pronounced than in former eras, but are still obvious in comparisons of high-end with entry-level instruments.
Lastly, the mechanical skill of the tuner is very important to the stability of the tuning. One of the greatest obstacles to tuning stability is the unequal tension that occurs between the vibrating and non-vibrating sections of a string as, during tuning, the wire is drawn over the friction points that separate those sections near the string’s two ends. As soon as the note is forcefully played, the tension will equalize and the string will go out of tune. To prevent this from happening during a performance or shortly after the tuner leaves, tuners use test blows — striking the keys at least as forcefully as any pianist would — to settle the strings so that they can be immediately retuned, if necessary, and stabilized. Another important mechanical skill is the ability to turn very tight tuning pins by minute amounts and without bending them — a bent pin will quickly unbend, and throw its string out of tune.
A highly skilled tuner working on a good instrument can tune so stably that when the humidity changes, most of the notes on the piano will seem to move sharp or flat together, and the tuning will continue to sound good for some time. In most cases, a skilled tuner can do a terrific job in 1½ to 2½ hours, sometimes less. Inexperienced tuners who take all day to tune a piano will move and bend the pins much more than necessary, producing an unstable tuning and possibly damaging the pinblock.
Electronic Tuning Devices vs. Tuning by Ear
Electronic tuning devices (ETDs) are now used by many piano tuners, even by some who can tune by ear. Unlike the aural (by ear) tuner, ETDs can “hear” only one note at a time; they don’t listen to intervals or beats, or tune the strings of a unison to one another. When using an ETD, it isn’t necessary to first tune a temperament. In theory, one could tune a piano with an ETD by starting at the lowest note on the piano and working upward to the highest.
A skilled tuner who has trained as an aural tuner can use an ETD to great advantage. The use of an ETD doesn’t eliminate the need for the tuner to develop superior listening skills, but it does allow the already skilled tuner to perform such tasks as pitch raising faster and more accurately, reducing the need to retune sections that have already been tuned. Use of an ETD also allows the tuner to tune for longer periods of time with less fatigue, and makes it possible to tune in noisy environments that would be difficult for an aural-only tuner.
For concert and recording work, an ETD is a more accurate pitch reference than a tuning fork, which can vary in pitch with temperature. This is particularly important when tuning a piano that will be accompanied by an orchestra, as many professional orchestras tune to a pitch of from A-441 to A-443, both of which are slightly higher than the traditional A-440 to which most pianos are tuned. (The numbers refer to the frequency, in cycles per second, of the A above middle C.) In an institutional setting in which two or more pianos must be tuned together, an ETD makes it easy to synchronize not only the overall pitch, but also the stretching of the octaves in the upper and lower sections of the keyboard.
Problems occur, however, when novice tuners without aural skills are entirely dependent on ETDs. They can’t hear when they make a mistake, or when they need to override the judgment of the machine to get the best results. Also, an ETD cannot, by itself, create a stable tuning. The tuner must still know how to manipulate the tuning pins and strings so that the piano will stay in tune when the job is done.