Voicing a piano

I attended a workshop a couple of weeks ago in Cambridge on the subject of hammer voicing, which is a way of changing the tone of a piano (it's sometimes referred to as "toning") - so I thought it might be a good time for a potted introduction to one of the important but slightly abstruse corners of the piano trade.

By way of explanation, it would first be worth mentioning that when a piano string vibrates, it doesn't just create a sound at one pitch or frequency. In fact, the string goes through a complex set of vibrations that create sound at approximately 2, 3, 4, 5 and so on times the frequency of the base (fundamental) note. This is one of the things that gives an acoustic piano a rich tone (difficult to imitate on an electronic instrument). Bass notes have more of these "overtones" than notes in the treble.

However, the prominence of these partials or overtones in the sound can vary from piano to piano; those where they are not very prominent are normally said to be "mellow" whilst those where the overtones are very prominent are "bright"; this may become "harsh" if the extra tones are too strong.

To overcome the problem of harsh (or excessively muddy) tone, it's possible to carry out different treatments on the hammers of the piano - however before doing this the piano needs to be in a good state of regulation and very well-tuned, paying particular attention to the unisons (that is, for most notes on a piano, there are two or three strings to increase the volume; these strings should be perfectly in tune with each other). If unisons are poorly tuned, this can give an impression of poor tone even if the hammers are fine.

The diagram above comes from Alfred Dolge - Pianos and their Makers (1910); this book is now in the public domain so can be read for free on the internet, and in this case illustrates a hammer-covering machine devised by the author in 1887. It shows the principle of hammer manufacture: a wedge-shaped block of felt (green arrow) is compressed around a set of hammer heads (red arrow), which is fundamentally the method still in use today. This means that the outer layers of the felt are under tension, the inner layers under compression.

For this reason, new hammers are sometimes "pre-needled", that is, treated with a larger needle to release some of the cupped layers of felt closer to the centre.

Piano hammers can then be sanded, using a strip of sandpaper pulled around the nose with pressure from the forefinger, to give an even surface. This method can also be used on pianos with hammers that have deep grooves in the nose from years of use (as long as there is enough felt left, particularly on the hammers in the high treble). Heavily grooved hammers can result in a dull or metallic sound with poor tonal quality.

Sanding hammers to ensure clean contact with the strings (the rear hammer of the two is the one being sanded)

It's then possible to carry out careful sanding on the nose of the hammers with a finer abrasive paper to ensure that the contact between the hammer and the strings of the trichord is even and perfectly simultaneous when each key is pressed.

Once all this has been done, the person carrying out the voicing will listen and assess the tone of each note on the piano, checking in particular for the following:

• Is the tone harsh (too bright) or too muddy across the piano or on certain notes?
• Is the tone even across the piano, or are there any changes (particularly sudden changes) of tone or timbre?
• Does the piano have a good dynamic range or is the sound too aggressive, and is the tone harsh when played loudly or softly? 

Carrying out needling of the hammers

The answers to these questions will inform the piano voicer as to the way in which the hammers need to be treated. This is quite detailed, but in general terms over-bright or harsh tone is dealt with by needling the hammers with voicing needles, which soften the surface of the felt. On the other hand, if the tone is muddy or dull (too mellow) then the surface of the hammer needs to be hardened a little. This can be done by sanding of the surface of the hammer, ironing with a specially shaped hammer iron, or treating the hammer with a special hardening solution.

Many thanks to Richard Schönhardt of Bechstein's, Chris Vesty who organized the day and to Millers of Cambridge for hosting such an excellent training session.

This informative video on YouTube shows a piano technician from Nevada sanding and voicing badly worn hammers on a Baldwin grand piano, and the difference that can be made when the instrument starts out with a poor or harsh tone.

Broadwood Piano Festival

I was very keen to write up my trip to the Broadwood Piano Festival in Whitby last Saturday - so here it is.

I set out on the 7.40 train from York to Scarborough on 4th June. Nice also to have my first close encounter of the musical kind at Scarborough railway station, which has acquired a "public piano" (along with a large number of others in the North of England, but unfortunately not York... harrumph!)

After arriving at Scarborough, thanks to Dr Beeching, I couldn't continue my journey any further by rail, so I ended up catching an absolutely packed bus which climbed an enormous hill out of Scarborough and passed across mist-shrouded moors before descending down another very big hill into Whitby.

Wonderful Whitby is famed for its history, scenery, olde worlde charm, tea rooms, sea air, steam trains and.... well, let's not mention the weather, shall we? At least it wasn't raining. It would be positively impolite to come this far and not take a walk up the famous abbey steps (all 199 of them) and see the famous Abbey itself, albeit in my case by walking around the back of the site. Thought you might like this photo:

Whitby Abbey in June

You can definitely imagine Dracula turning up near here around nightfall, can't you? In any case, on with the journey to Lythe village, about four miles out of Whitby to the north, where the festival was being held. The name of the village comes from a Scandinavian word for "slope" - I'll leave you to guess why that might be but if you really want to know, try walking up the road from Sandsend, just up the coast from Whitby, into Lythe village itself. The Piano Festival was a two-day event at the village hall. 

This was the oldest of the pianos on display, a 1793 Broadwood square piano, and still in working order after 220 years.The first thing to note about square pianos is that they aren't square - in fact the term (according to the Piano History Centre) comes from a corruption of the German term "Querpiano" which, as my German housemate pointed out, means exactly the opposite (transverse or "skew-whiff" piano) which refers to the position of the strings, which run diagonally across from side to side (unlike a grand piano where they run directly back from the keyboard). In fact, Germans now use the term Tafelklavier ("table piano") for this type of instrument which is a very apt description.

The tone and touch of the piano is quite delicate by modern standards and it sounds not unlike a harpsichord (though, unlike a harpsichord, the finger can control the strength of the blow and thus the volume). By the middle of the next century, a desire for more volume, sustaining power and a resonant tone had led to the piano becoming much bigger and heavier:

This is an 1858 Broadwood square piano - in case you're wondering why there's a picture of Queen Victoria on the music stand, it's because the piano belonged to her - it was moved into Buckingham Palace in 1867 as shown in the documents in the open folder on the right-hand side. In fact this is well towards the end of the era of the square piano since production in Europe finished not long after 1860. During the late eighteenth and early nineteenth centuries, the square piano had been a smaller and less expensive instrument than a grand piano, better suited to limited spaces. However, by this time the size had increased to a point where moving the piano was a significant challenge - like a grand piano, this one would need its legs removed and to be tipped on its side when moved. 

By now the square was in competition with the upright piano, which took up less floor space and was much easier to move than the larger squares then in production. In addition, the position of the action in square pianos (positioned behind the keyboard) and the limited space for it meant that hammer shanks were of different lengths and hammers had to be specially shaped and angled, in contrast to the upright piano where shanks could be of relatively uniform length and hammers of much more similar dimensions. This meant that square pianos were relatively expensive to manufacture, so they rapidly disappeared from the market. Curiously, they persisted much longer in the American piano industry, with Steinway's continuing to produce them as late as the 1890s - later examples continued as before to grow in size and gained full cast iron frames.

Also the sustain pedal of the piano can clearly be seen - Broadwood was one of the very first manufacturers to use these in place of the older knee pedals or hand stops in the 1780s.

This piano is an early barless grand made by Broadwood, with a pressed steel frame - the section of the rim with the red and gold decoration is also part of the frame. The piano is straight-strung (later barless models were overstrung). Unlike conventional piano frames with bars, this type of frame, an innovation of the Broadwood company, cannot be made of cast iron, because of the significant flexing that takes place when the substantial tension of piano strings is placed across it. This movement would cause a conventional cast iron frame to crack (as the material is strong in compression but relatively brittle in tension).

The grand piano above is a later barless model from around 1920, which is overstrung. Both of the barless models in fact have a remarkable continuity of tone from bass to treble (across the break in the case of the overstrung) but unfortunately the cost of the cast steel required made them much more expensive than conventional frames, especially after the First World War when materials were scarce. In typical fashion, one of the bass strings on this piano had broken a couple of days earlier, at which point it was too late to have a replacement made before the Saturday evening concert! One other unusual feature is that some of the copper-wound strings in the upper bass are trichords (normally there are two strings or only one for these bass notes).

Congratulations to Dr Alastair Laurence of Broadwood and his dedicated volunteer team of piano technicians and helpers (Cristina, Heather, Heather, Yo, Steve and Geoff to name those I know of) on a fascinating exhibition and all the hard work to bring these pianos into a good state of repair beforehand, as well as staging the whole event itself. A great shame I had to miss the two concerts on the Saturday and Sunday evenings as it would have been impossible to get back to York afterwards, but a fascinating and worthwhile day out.

Broken strings

Broken Strings

Let's suppose you have stepped into a time machine which has transported you back to the year 1875. You are walking down the main street of a frontier town in the American Old West, when you hear a loud bang coming from the saloon bar, after which the tinkling of the piano falls silent. Should you:

(a) Pelt down to the local sheriff's office as fast as your legs will carry you to warn everyone that the Coyote Kid and his band of outlaws are back in town or;
(b) Send for a piano tuner?

The answer is - b (well, possibly).

I recently read an article on the internet, on the subject of myths about the "Wild West". It mentioned that guns were not nearly as ubiquitous as you might suppose if you learnt about the period from John Wayne films; many towns and cities had rules prohibiting the carriage of firearms. So if you heard a sound like a gunshot coming from the saloon it might not be a six-shooter going off but... the sound of a string breaking on the piano.

In the mid-19th Century it was not uncommon for piano strings to break when the instrument was being played, although more usually when subject to a virtuoso attack. Franz Liszt (1811-1887) was famous not only for breaking strings in prodigious quantities in concerts (apperently people would fight over them as souvenirs), but sometimes even for cracking the case of the instrument! Fortunately modern pianos are much more robust than in Liszt's time, with cast iron frames and piano wire much improved from that used in the past; however even today, it is not unheard of for a string to break while being played (though it is fairly rare).

Piano strings, under high tension, can also occasionally break in the course of a tuning and they do go off with rather a spectacular bang. For this reason, if you're very nervous (should I say highly-strung?) don't try and tune a piano. However, as I've had a few jobs recently that have involved replacing strings, I thought I would explain a bit about why they break and how they can be replaced.

Why do strings break?

Piano strings are made of high-grade steel wire, which is normally just polished (sometimes plated). The thicker bass strings have copper windings around a steel core.

The most common cause in my experience is pianos that have not been tuned for a long while and/ or have rust on the strings through being stored in a high-humidity environment. This can mean that oxidation can build up between the string itself and the bearing points (e.g. pressure bar, agraffe or the coil itself on the tuning pin) so that instead of the string sliding smoothly, it "catches" on the rusty surface and then breaks. This can sometimes (not always) be overcome by taking the string down in pitch before raising it. Of course the rust can also just weaken the wire to the point where it snaps anyway.

It is also possible, but less common, for pianos with no visible rust or oxidation problem to break, which may be due to defective manufacture of the wire; sometimes the wire seems to get "fatigued" on certain pianos for no especially obvious reason. Occasionally you can get several breakages on the same part of the same piano, which is likely due to the batch of string that was originally used.

How are strings replaced?

A competent piano technician should be able to replace a broken string for you. I normally make a special visit since there are around 20 gauges of steel wire commonly used in pianos and it's not practicable to carry them around on the offchance they'll be needed - however I do keep commonly-used gauges in stock at home. I will measure a broken string with a micrometer to find the correct diameter, then bring wire of the correct gauge with me.

 Piano string comes in half-kilo reels

Bass strings (with copper windings) are a special case since they cannot be replaced with generic wire - the string must be specially made to order by a string maker which is much more expensive (commonly around £25 each).

Breakages are most common on the treble strings, where the wire is at a tension closer to its theoretical breaking strain than in the tenor and bass; but strings can break in any part of the piano.

Replacing the strings involves carefully winding out the tuning pins and coiling a new piece of wire onto the them. Replacing a treble string, or fitting a new copper-wound bass string, is usually reasonably straightforward, but if the note is in the tenor area of the piano, where the steel strings normally extend underneath the bass strings (overstringing), it can be a longer and more fiddly job.

If a string on your piano breaks whilst you are playing, save the old string since the piano technician will need to measure it to find the correct replacement. If it has been lost, then its dimensions can usually be estimated by measuring the strings next door to it.

Do piano tuners normally charge for replacing broken strings?

Must tuners (myself included) will normally charge for replacing a string because it's part of the normal ongoing maintenance of your piano, and not something that can be avoided completely however skilled the tuner is. In instances where there is a high risk of breakages (such as pitch raises on pianos that have not been tuned for many years, or where there are rusty strings), I will normally mention this risk at the beginning. The charge for bass string replacement is greater because of the cost of ordering the strings.

Feeling the stretch

Another issue when replacing the strings is that new ones will invariably stretch appreciably after being first fitted, so it may take some time for the tuning to stabilize on the affected note(s). This can be alleviated (but not eliminated) by using a string stretcher, which is a tool with a small wheel that can be run up and down the string. This "pushes" the wire and causes the stretching process to take place more quickly. Unfortunately this method can't be used on the copper-wound bass strings.

A string stretcher (right) with a coil lifter and stringing hook, two other tools used in restringing

Anyway, the video below really has nothing whatever to do with broken strings but I thought that as Franz Liszt got a mention it would be an appropriate segue into my favourite four-hands rendition of the Second Hungarian Rhapsody, performed by Victor Borge and Sahan Arzruni:

Honky-tonk piano tuning

I recently got asked about honky-tonk piano tuning. Honky-tonk was a style that was extremely popular, on both sides of the Atlantic, from the early 1950s until the 1970s. Jim Hession gives a great explanation of it in this video from You Tube.

Popular exponents of this style in Britain included Winifred Atwell and Mrs Mills. The music was frequently played on pianos that had been specially tuned or treated in some way to give the impression of an old, out-of-tune upright.

The heyday of honky-tonk piano has long since passed so the question doesn't arise very much, but it is possible to achieve this effect using the following methods:

• What NOT to do: Sticking drawing pins in the hammers was a favourite old trick to give a tinny, metallic sound. This isn't a good idea for the future life expectancy of your piano - when the drawing pins are removed the holes soften the felt which will give a "cotton wool" effect to the tone of the hammers (rather like a very bad voicing), and if they're left in they can eventually end up splitting the felt so the hammer head falls apart.
• A few pianos were built with a "mandolin attachment" which consists of a piece of flexible material (normally felt) with metal tabs attached to the end of each one, which is inserted between the hammers and the strings (it would also be possible to install one of these manually if not already fitted). Although not as bad as drawing pins, this might still deform or damage the nose of the hammers in prolonged use, so at best should be employed sparingly.
• It's possible to treat the hammers with a hardening solution; this will give a brighter, harsher sound which is reminiscent of what happens when normal hammers become grooved through many years of use. This method won't cause any harm to the piano, but is irreversible unless you want to spend several hundred pounds having all the hammers replaced.
• Finally, the safest method is to ask a tuner to de-tune the unisons for you. Firstly a conventional tuning is carried out, then for all the bichords and trichords, one of the two or three strings is moved slightly out of tune (perhaps about one or two beats). "Subtle" is generally the better option here. This won't do any harm at all to your piano and is completely reversible at a later date (although you'll have to call the tuner again if you get fed up with it).

Personally I enjoy this type of music, although given the choice I prefer to hear it on a conventionally-tuned piano, or at least one where the honky-tonk effect is not too over the top.

To round off, here's a video of the wonderful Mrs Mills appearing with Eric & Ernie in 1971:

Pianos and humidity

From time to time I get jobs that involve fixing loose tuning pins on pianos. The pins (which maintain and control tension on the strings) are generally between 50 and 65mm long and are driven into a thick piece of wood called the wrest plank.

The reason I mention this is to raise the topic of how humidity can affect your piano. Although temperature changes can make a difference, a piano is likely to be fairly happy as long as the variation isn't too extreme. More problematic are changes in humidity - specifically relative humidity (the amount of water vapour in the air as a proportion of the saturation point at any temperature). Relative humidity can easily be measured using a hygrometer - these can be purchased very inexpensively from shops or on the internet (left-hand picture shows an analogue type, the right-hand one a digital; these are both combined thermometer/ hygrometers). Hygrometers generally need to "settle" in a room for a certain length of time before giving a true reading.

Generally speaking, pianos are happy with relative humidity in the central range (40 to 60%); allowing humidity to get lower or higher than this for long periods may cause problems. In practice, high humidity conditions can occur when pianos are stored in locations such as unheated outbuildings or the piano is in a damp or cold place (possibly close to a poorly-insulated outside wall). Low humidity however is a more common problem in modern centrally-heated houses because during the winter cold air from outside is heated without adding any moisture, so the relative humidity drops very rapidly (warm air can hold much more water vapour than cold air). For example, if air at 4ºC is taken in from outside at 80% relative humidity and heated to 22ºC inside the house, the humidity level drops to just 25%.

Common symptoms of low humidity conditions (35% relative humidity or less) are:

• Loose tuning pins due to drying out of the wood in the wrest plank. These can sometimes be fixed, but tuners will charge for doing this and in some cases may have to install a new string since the pin may need to be removed to fix the problem
• Soundboard (and sometimes other wooden parts) may start to crack or split

An important point to note is that older pianos (because of the materials used) are generally much less tolerant of very dry conditions that newer ones. If you can't keep your piano in a cooler place and a fairly long way from radiators during the winter, then consider getting a more modern instrument.

Problems that may be associated with damp (over 65% relative humidity) conditions are:

• Film of rust may appear on steel strings and tuning pins, and verdigris on copper
• Mildew on wooden parts
• Veneer peeling on case
• Keys and action parts sticking or sluggish
• Problems can result when the piano dries out (e.g. things coming unglued).

Alleviating the problem of very low humidity

• If a hygrometer shows there is a problem, consider putting the piano into a room other than the main living room (dining rooms are a popular choice) where the heating can be kept on a slightly lower setting during the winter
• Otherwise see if you can turn the heating down a little generally
• Keep the piano some distance away from any radiators or other direct heat sources
• Keep it out of direct sunlight if possible
• It is possible to purchase humidity control systems, though these are only likely to be a sensible investment for more expensive pianos.

Leaving a jar of water laying around in the room will not be enough to make any significant difference to the humidity, though putting it inside the base of an upright with the top closed might just be enough to help a little - however if you do, remember that it's there when you move the piano and don't spill it or it could cause damage.

Oddly enough, allowing the temperature to fluctuate a little more in the room (cooler in winter and warmer in summer) may help to moderate the humidity variations that are so bad for your piano. 

"Standard" or "concert" pitch - what is it and is my piano tuned to it?

What is generally referred to as either standard or concert pitch is an absolute frequency to which a reference note is tuned on pianos or other instruments. The note which is always used as a reference is A above middle C (A49 on a piano), and the standard pitch for this note is 440Hz.

440Hz was agreed as a standard at an international conference in May 1939, and was adopted in 1955 by the International Standards Organization (ISO 16). It's used in most parts of the world, including Britain and North America; however some European countries (informally) use higher-pitch tunings such as A=444Hz.

Very often when out tuning I come across pianos that are a long way below this - sometimes a semitone or even a tone lower. Generally, these are older pianos where the pitch has drifted down over a period of many years of sometimes irregular tuning. To bring these pianos up to pitch requires the tuner to undertake two operations - firstly a fast rough tuning to get it close to the required level, then a fine tune to get the notes at exactly the right pitch. Because this is a more complex and time-consuming job than a standard fine tuning (just doing the piano once), most tuners will quite reasonably charge more money for the service.

If you have a piano that is well below standard pitch and you're having it tuned, the first question to ask is whether you would like it brought up to pitch. Any piano can be tuned perfectly well to itself, and leaving a piano below pitch does not damage it in any way, although the tone may arguably not be quite as good. What are the considerations for doing this?

There are some (generally older) pianos where a pitch raise may be inadvisable, due to the condition of the instrument (e.g. if the strings are rusty, there is a risk of breakages). A tuner should be able to advise on whether it is a sensible idea to attempt this, although it should be possible with most instruments in a reasonable condition.

Assuming the piano is OK to have its pitch raised, the following are important reasons for getting an instrument to pitch:
(i)    Playing with other instruments (which will be tuned to A440)
(ii)    Singing with the piano to a high standard
(iii)    Playing along with recordings.

If the piano is used solely for individual practice (or singalong-type singing), there is no imperative need for it to be on pitch, though many pianists prefer it to be nonetheless.

If I come across an instrument well below pitch, I will always ascertain the needs of the customer and check before carrying out a pitch raise. I am perfectly happy to tune a piano at a lower pitch (normally cheaper) if this is a better option for the owner. Additionally, if the piano is subsequently regularly tuned, there is an option to raise the pitch in small steps.

One point to note is that if a piano is already at standard pitch and kept regularly tuned (generally at least once a year), the tuner should "nudge" the tuning of the piano very slightly up as needed to keep it there; under these circumstances there's no excuse for the tuner to allow it to go flat.

Aural vs electronic tuning - which is better?

One of the questions I sometimes get asked on my rounds is about electronic tuning devices (ETDs) for piano tuning - do I use one and are they any good?

The picture above is of a Korg OT-120 chromatic tuner, which I'm "testing" with a tuning fork. In my opinion it's one of the best chromatic tuners out there. I use it to set the first string when tuning a piano, to check the piano is on pitch (although I can tune to a fork, it takes a little longer). This is the only piece of electronic equipment I have.

After this, the electronic tuner has done its job and gets put away - it can't be used to tune a whole piano - and I complete the entire remainder of the tuning by ear. This isn't because of any fault with the tuner itself - rather it's because of the way piano strings behave.

When a string vibrates between two fixed points, it vibrates separately through portions of its length (whole, half, one third, one quarter, one fifth and so on), which create additional tones (called overtones or partials) in addition to the fundamental frequency. Thus, A below middle C, which should have a frequency of 220Hz at standard pitch, will also produce overtones at 440Hz, 660Hz, 880Hz and so on.

However, because a piano string is slightly stiff and not perfectly flexible, the overtones actually end up being slightly higher in pitch than they theoretically should be. When a piano tuner is putting the instrument into tune, (s)he is actually matching the overtones of lower notes to the fundamental pitch of higher notes. This leads to the phenomenon of "stretch" - the octaves on a well-tuned piano are actually wider than they theoretically should be. The reason for doing things this way is simply that the piano sounds better. When tuning aurally, the ear listens for these consonances and stretches the tuning automatically (after proper training).

This brings us back to the question of the tuning devices. The Korg is a chromatic tuner which gives us theoretically correct frequencies, so if we used it to tune a whole piano, the "stretch" would be missing. Most people agree that a piano tuned this way sounds pretty awful!

However, there are some modern software applications that are able to sample the sound of the piano and calculate a suitable stretch. Most of these applications cost from a couple of hundred pounds upwards. This is the point where the controversy starts.

Which is the better method?

Some people claim that the aural method gives a better tuning because the electronics can never replicate the human ear. Others actually claim that "electronic/ computer accuracy" is better than aural tuning; which is correct?

The first thing to understand is that the ETD is a tool for tuners, not a tool that makes someone a tuner. There are other important parts of tuning technique, for example tuning unisons (most notes have three strings) and almost everyone agrees that the only way to get really good unisons is by ear. This is a tough enough job in itself.

Although I don't use one myself, I believe that ETDs have sometimes acquired a much worse reputation than they deserve, due to the misconception that they will allow someone with no skill and experience to tune a piano. In the hands of capable technicians, some of whom do use these devices, excellent tunings can be produced. However, in these cases, the technician is using experience and skill, listening to the tuning in conjunction with the ETD, to get a good result. Some tuners find they are able to achieve good results more quickly in some circumstances with this method.

Simply trying to tune by looking at a needle without listening to notes and intervals does NOT give good results. Any skilled tuner should be able to listen to and appraise the work they have done, to check what the electronic device is telling them is correct. Tuning a piano is about making it sound good, not about pegging it to a set of mathematically "correct" frequencies.

My reason for not using an ETD is a personal one - when I'm tuning, I just find it a distraction. This is a comment on me, not on the quality of the equipment.

Conclusion: some skilled tuners use purely aural methods and some use electronic tuning devices. Either method is fine, but the tuner must have the skill and experience to be able to listen to the work they have done and check whether it's a good tuning or not.