As presented by Ron E. Overs
The proliferation of quality sound equipment and other electronic instruments has increased the public's awareness of the need for accurately tuned instruments, including pianos. Consequently, the demands on the piano technician to perform to a higher standard, are perhaps greater today than in previous times. The skill of the piano tuner is a major factor contributing to good tuning stability. However, good piano scale design, quality of construction and housing conditions are also highly influential factors
The skills required for piano tuning
Understanding the problems of tuning
The difficulty of mastering tuning hammer technique
When tuning, do we turn the tuning pin, or bend it?
Setting the tuning pin
How hard should the note be struck?
Good tuning technique maintains a quality tone
Should we tune seated or standing?
Should we tune with the right or left hand?
Excessive friction at the bars/stringing felt
Temperature transients, the effect on tuning stability
Humidity transients, the effect on tuning stability
THE SKILLS REQUIRED FOR PIANO TUNING
A significant proportion of the population has the ability to hear whether a note is 'sharp' or 'flat'. Of that proportion, a small percentage has the ability to perceive beats between discordant unison strings or intervals, with an ability to determine the beat speeds of related intervals. But, it is the ability to manipulate the tuning hammer, and the fine motor skill required there which determines, to a major extent, the ultimate level of skill of the piano tuner/technician.
UNDERSTANDING THE PROBLEMS OF TUNING
If one were to overhear two piano technicians discussing their work, one might expect to hear reference to the term 'setting the pin'. Experienced piano tuners are well aware of the need to use the tuning hammer in a manner, which has been shown by experience, to ensure the best possible tuning stability. The term 'setting the pin' should really be called 'setting the string', as it is the tension equality of the segments of a unison string which will determine the stability or otherwise, of a tuning. It is desirable to achieve, as far as possible, equal tension on all segments of a tuned string. The problem confronting the tuner is that the string speaking length, ie. the portion between the agraffe/capo' bar and the first group of bridge pins, is the only segment which provides useful information (about the tension) to the technician, by way of its pitch. The tension of the other segments (tuning pin to duplex bar, duplex to capo' bar, and bridge to hitch pin), will not necessarily be the same as that of the speaking length. Friction at the bars/bridges which divide the string segments, causes the string tension to vary with respect to the tension of the speaking length, as the pitch is moved up or down. Correct tuning hammer technique can, to a large degree, overcome the problem of variable string tension in the string segments. For example, when tuning a unison string which is quite 'flat', the tuner will pull the pitch of the note higher than 'in tune'. The degree of sharpness required will always be a matter of experience. This will pull up the segment of string, between the hitch pin and the bridge, to the approximate tension of the speaking length (when it is 'in tune'). If the string had been pulled to pitch without firstly pulling it 'over pitch', the friction between the string and the bridge would ensure that the tension of the bridge to hitch pin segment remained lower than that of the speaking length. In general, the first pitch movement of any string, when tuning, should be to the 'opposite side' of tuned pitch. The degree of 'sharpness' or 'flatness' of this string movement will depend, to a large degree, on how far away from 'in tune' the string was initially.
If a piano is close to 'in tune' initially, then the strings should be moved an appropriately small amount. Even a skilled tuner cannot hope to achieve real equality of tension for all of the string segments, only a close approximation. After tuning, any significant tension inequality of the various string segments will tend to equalise over time. This is the major reason why a previously poorly tuned piano loses its tune rapidly after a tuning. Further, it is also the reason why a previously well tuned piano, subsequently carelessly tuned, rapidly loses its tune. On a couple of occasions in my own career, a concert grand piano, previously in a fine state of tune, was subsequently tuned by a 'concert' technician who dragged the strings all over the place as if he were doing a pitch raise. Apart from removing the tuning which was in the piano previously, the tuning stability was very ordinary for a month after, requiring three tunings to return the piano to a state of stability.
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THE DIFFICULTY OF MASTERING HAMMER TECHNIQUE
I have taken several students through the agony and frustration of learning to tune. I say agony because, in my experience, the task of making the transition from novice to proficient tuner is one of the more arduous in the music industry. For those who finally make it, it is a real achievement. Many students, regrettably, fall by the wayside. (It is of even greater regret perhaps that some of them have, in the past, kept on 'tuning' long after they have fallen).
There is much diversity of opinion throughout the profession. Should the tuner stand or sit? Should the tuning hammer be held with the left or right hand? How hard should the note be struck when 'setting the pin'? It is worth taking time to consider the fundamentals of 'good' tuning practice.
WHEN TUNING, DO WE TURN THE TUNING PIN, OR BEND IT?
Unfortunately, there are many in our profession who are inclined to bend the tuning pin instead of turning it, when a major change in pitch is required. This 'easy' approach is extremely harmful to a piano. A piano in commercial service will probably be restrung at least once during its operational service life. When such a piano has been tuned repeatedly by a 'pin bender', the effect of destringing will be to damage the pin block severely. The bent pins, when wound out of the pin block, will 'bell-mouth' the tuning pin holes. The worst of these holes will require plugging.
When we rebuilt a Steinway D for the ABC in 1992, some severely bent tuning pins had to be straightened to allow for their removal. Twenty five tuning pin holes required plugging prior to restringing the piano.
'SETTING THE TUNING PIN'
When a string is significantly out of tune, the first step will be to turn the tuning pin (without bending it), moving the pitch to just the other side of 'in tune' pitch. Then, applying a small amount of pressure on the tuning hammer (in the same plane, as when turning the pin, but in alternative directions), the pitch may be moved slightly up and down. The applied pressure on the tuning hammer causes the tuning pin and the pin block to 'spring' a small amount, allowing for such small pitch changes as will be required to complete the tuning process. If the tuning pin was initially turned to the correct position, it will be possible to change the pitch of the string (by 'springing' the pin), equally above and below 'in tune' pitch. If this is not possible, the pin should be turned again, and the technique of springing the pitch repeated, solidly striking the note and rechecking, until the tuner is satisfied that the string is finally in tune, and that the tension has been equalised for each string segment. It is this combination of firstly turning the pin, then gently flexing the pin over and below pitch while solidly striking the note, which facilitates the achievement of real tuning stability.
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HOW HARD SHOULD THE NOTE BE STRUCK?
The concept, of solidly striking the note when 'setting the pin', is intended to insure that the string does not move out of tune under heavy playing. When a note is struck, there is a momentary increase in the speaking length tension as the hammer strikes the string. If the tension of an adjacent string segment is lower than that of the speaking length, the piano wire might move from the adjacent segment into the speaking length, moving the note out of tune. Obviously, the softer the tuner strikes when setting the pin, and the harder the piano is played by the pianist, the greater the risk of losing tune. One could argue, therefore, that it is always better for the tuner to strike as hard as possible when tuning. However, striking the piano heavily will contribute to early fatigue of the wire, while increasing the risk of broken keys and hammer wear (with subsequent deterioration of the voicing). I suggest that a sensible approach might be to strike quite firmly, varying the intensity in accordance with the performance habits of the pianist. Prior to tuning a concert piano, I seek the name of the pianist, and how hard he/she plays. Using this information, when tuning for a player who does not thrash the piano, I can strike moderately hard, looking after the piano wire and voicing. When tuning for a known 'thumper', I can modify my technique striking more heavily, concluding with a rather sore hand. But, at least, the piano will stay in tune during the performance. Mind you, there are some pianists who play so heavily that they will destroy a tuning, no matter how well it is set in place.
A skilled tuner tuning a regularly serviced piano, will move the strings very little, and the pins even less. It is most important that the strings are moved as little as possible during the tuning process. Piano wire, an alloy steel comprising 0.85% carbon, with a nominal hardness of 45 Rockwell C, can stand only a certain amount of bending. When a tuning pin is turned, the wire bends at the tuning pin, and at the capo' and duplex bars. If the tuning pins are turned excessively when tuning, the chances of breaking piano wire, in the long run, are greatly increased. I believe poor tuning technique to be the greatest contributing cause of broken wire on pianos in commercial service. I have just concluded an experiment, over the past three years, which fully supports this proposition.
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Pitch raising is similar in many respects to normal tuning, However, additional considerations must be allowed. Firstly, the pitch change required may be an order of magnitude greater than for a normal tuning, therefore, the frame will flex considerably under the increased strain (often several tonnes in total). Consequently, the string will need to be pulled further over pitch, and tuned sharper (in certain areas of the scale) to allow for the resultant pitch sinkage. This will occur as the frame and soundboard settles. Judging the correct amount of 'pull over' is a matter of experience; such factors as the design of the piano, the frame rigidity at each section (the frame will flex more at the centre of each section where there is less support, requiring more 'pull over'), the amount of down bearing on the soundboard, will guide the experienced tuner to complete a pitch raise more efficiently.
GOOD TUNING TECHNIQUE MAINTAINS A QUALITY TONE
Many of those who listen to piano performances and recordings will hear a metallic noise, 'string noise', on some notes (particularly common on pianos which have seen much use). This noise, produced at the onset of tone when a note is played, is caused by the shape of the duplex and Capo' bars on the iron frame; a larger than desirable radius allows the strings to 'buzz' on the frame bar. Duplex and Capo' bars should be shaped with a small radius at the apex of the bar to ensure a 'clean' sounding note (this will establish a smaller point of contact between the bar and the string). Irregularly shaped bars (ie large radius bars) will allow the string a greater length of contact with the bar, encouraging the development of 'string noise'. The frame bars and agraffes on frequently tuned pianos are subjected to a great deal of abrasion as the piano wire is moved during the tuning process. The wire cuts a groove into the bars, which frequently facilitates the development of string noise. The greater the string movement when tuning, and softer the frame metal, the faster will be the development of string noise. Therefore an experienced tuner, moving the strings less, will contribute to the maintenance of quality piano tone.
Modern piano frames are poured using foundry techniques which enable slower cooling of the cast iron than previously. While this has resulted in improved castings, lowering the internal stress in frames, they also tend to be softer, allowing increased string abrasion on the bars. In recent years manufacturers have been experimenting with techniques of hardening the frame bars.
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SHOULD WE TUNE SEATED OR STANDING?
This matter was raised during 1995 at a workshop in Sydney on Tuning Hammer Technique. Taller technicians will damage their backs bending down to the piano when standing, while others cannot effectively reach the pin block from the seated position. After some discussion it was generally agreed that this should be a matter of choice for the individual. We wouldn't want technicians to suffer under the effects of using a tuning hammer would we, or some caring soul might call for the establishment of a national register of tuning hammers.
SHOULD WE TUNE WITH THE RIGHT OR LEFT HAND?
There are purists among us who maintain that upright pianos should be tuned using the left hand, and grand pianos using the right. I believe we should tune pianos with the hand which allows us to tune to the best of our ability. Generally, people who are left or right handed are poorly coordinated with the other hand. This matter of prejudice regarding hand preference has developed out of a fear of bending tuning pins. If you think about your tuning technique you will not bend pins, regardless of which hand you use.
OTHER FACTORS WHICH AFFECT TUNING STABILITY
Other factors which influence tuning stability cannot be considered in isolation. A piano will always hold tune better when tuned by a skilled tuner, but stable temperature and relative humidity conditions will also increase the likelihood of good tuning stability. On the other hand, poor scale design and ordinary construction, will dramatically reduce the chances of a piano standing ' in tune'.
EXCESSIVE FRICTION AT THE BARS/STRINGING FELT
After several years of service, and under certain conditions, the friction between the strings and the bearing cloth (immediately adjacent to the pin block) increases to the point where the movement of the string becomes erratic. The first symptom of this problem is that the pitch of the note fails to respond uniformly as the tuning pin is turned. In extreme cases, the string appears not to move at all, then jumps dramatically. These pianos are not only difficult to tune, but also exhibit very poor tuning stability. The only proper solution to this problem is to restring the piano and replace the bearing cloth.
When rebuilding, check that the original bearing cloth is not too wide (Bechstein grands often develop tuning problems from wide bearing cloth), narrower felt is better as it has a reduced tendency to bind the string as the piano ages. Duplex and capo' bars can be reshaped to a small radius to good effect. Since 1994, we have been heat treating (hardening) the duplex and capo bars to improve their durability in service. This process has allowed us to reduce the height of the bars when required. Our latest rebuilds, with reduced height, small radius hardened bars, appear to be producing the cleanest trebles we have heard anywhere to date (Please note, David Kinney did a class at the last Melbourne convention on reshaping bars).
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The two most important natural 'enemies' of piano tuning stability are variations in temperature and relative humidity. The effects of both can be minimised by careful scale design and manufacture, and sensible placement of the instrument in the room.
A) TEMPERATURE TRANSIENTS
The piano's strung back is made primarily from wood, cast iron and carbon steel. These substances all expand and contract with changes in temperature. Fortunately, the coefficient of expansion of cast iron (the frame) and carbon steel (the strings) is approximately the same. However, good tuning stability is also dependent on the piano wire remaining within a certain range of its percentage of breaking strain across the compass of the instrument. If a section of stringing has a lower percentage of breaking strain than the remainder of the piano, then this section will exhibit poor tuning stability. Unfortunately, many pianos have sections with large variations in the percentage of breaking strain. The area of greatest variation is usually at the lowest notes on the treble bridge. It is here where most pianos are at the greatest risk of tuning instability. The tuning stability of an upright or grand piano is usually directly proportional to its height or length respectively. It therefore follows, that we would expect concert grand pianos to exhibit the best tuning stability. In general, experience bears this out. Over recent years, we have seen the appearance of pianos of much better scale design, which are far less prone to this problem. Some designs have considerably less variation in the percentage of breaking strain of the string scale. For example, it no longer follows that a seven foot grand piano should always break from the bass section at F21 (like a typical concert grand). Some designers are taking the courage to move the break up; eg Yamaha's C7F, where the first plain wire on the treble bridge is G#24 (previously F21). The tuning stability is better for it.
We should, in the course of our regular work, always be on the lookout for those pianos which have good inherent design. Pianos which do not hold tune are a 'nightmare' for the pianist and technician alike. I have returned to a recently tuned piano on many occasions, to find that it has lost its tuning due to the influence of climatic factors on a poorly designed instrument.
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B) HUMIDITY TRANSIENTS
The piano soundboard is held securely around its perimeter by the case of the piano. The soundboard is manufactured with an upward curvature, crown, in the centre of the board. The crown approximates an arc of a circle of 18 metres in radius.
The strings pass over the bridges, turning with an angle of approximately one degree, towards the soundboard, at the back length. This produces a small down bearing force of approximately 1.4 Kg (3lb) per string, on the soundboard.
The soundboard crown effectively forms an arch, in section, allowing the soundboard to withstand the total down bearing force (up to 320 Kg) much more effectively than it would by its sectional dimensions alone. Variations in relative humidity will cause the belly wood to expand and contract, which will in turn cause the soundboard crown to increase and decrease. This will have an influence on the tuning stability of the piano; as the bridge height varies in response to the changes in soundboard curvature, the string tension will vary.
The hygroscopic expansion and contraction of the belly wood is also be affected by the way it has been milled. Quarter sawn belly wood will expand and contract with humidity changes 25% less than wood cut on the cross. Less soundboard movement will result in less change in down bearing pressure. Tuning stability will be improved. Therefore, sound boards made from fully quarter cut boards will allow for much greater tuning stability, compared to sound boards containing cross cut boards.
An increasing relative humidity will cause the soundboard crown to push harder against the strings at the bridges, increasing the effective soundboard crown. Therefore, the pitch of the piano will rise as the humidity increases, and vice versa. Unfortunately, this pitch change will not be uniform across the instrument. The variation in the percentage of breaking strain will alter the degree of pitch change in response to the variation in soundboard crown. The pitch change will be inversely proportional to the percentage of breaking strain, ie. the effect on pitch will be greatest on those strings with the lowest percentage of breaking strain.
It therefore follows, that the piano with the least variation in percentage of breaking strain will be the piano with the greatest tuning stability, with respect to relative humidity and temperature changes.
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When we consider the influence of the above mentioned factors on tuning stability, and their interdependence, we also gain a better understanding of what we should be expecting of ourselves, and of the piano manufacturers.
In the course of our regular working lives, we should always endeavour to improve the way things are done. In this way, not only will we be paid for our labours, but we will be rewarding ourselves, knowing we are doing our job better. Perhaps it's almost like getting paid twice.
Ron E. Overs 1996
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First published, 11 December 1998
Copyright © 1998, Overs Pianos.