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What is a false beat?

One of the most difficult and aggravating things that a piano tuner faces is what are called “false beats”. These occur when a single string produces a sound pulse that basically sounds like two strings that are out of tune. Each individual string should ring clearly as a pure sound with no distortions. Less expensive pianos tend to have more false beats, but they can occur in any piano of all ages and levels of quality. As pianos age, many strings, particularly in the upper treble section, tend to develop these false beats.

Many professional pianists or musicians generally have a limited knowledge of tuning. This issue is due to the fact they there are rarely any tuning courses offered in music schools. These courses are simply are not a part of most music degree programs. Pianist’s experience of tuning comes from listening to recordings or going to concert halls, where high-end concert grand pianos are tuned more often – sometimes daily. While this does provide a reference to the ear for what is well tuned, it does not give the academic and scientific base for understanding tuning. I have found this to be a disappointing shortcoming. I can also testify, given that I have a music degree in Piano Performance, that musicians often hear tidbits of information that are often not correct and lack the over-arching complete knowledge of a given aspect of tuning. This leads to a wild assortment of statements that often confuse the subject even more. I personally was so frustrated by contradictory statements by my fellow students and even teachers that I requested a course be designed for me while I was studying. I was fortunate to have an excellent tuner on staff and a dean that was willing to make the course possible. I also took elective courses in physics and acoustics to augment my musical education – these were NOT required for my music degree!

The single element than most musicians can hear most easily is the beats in the mis-tuned unisons (2 or more notes of the same frequency) or octaves which when tuned properly should not any beats. Beats essentially occur when strings are off by a faction of rate of frequency. For example, one string might have a frequency of 100 cycles per second and a second string a frequency of 101 cycles per second. In this case, the second faster frequency would catch up and pass the slower frequency causing the amplitude (loudness) of the sine wave to increase. This is what is called a beat. Without making this an involved lesson in acoustics, the effects is like turning the volume control on a pure tone to a higher volume level for a second and then back to the level it started at, and repeating this again and again.

The reason for the presence of false beats is not easily understood. Logic would suggest that something is changing in one or both of the strings sounding the same frequency in order for a beat to occur. Any change in the length of the wire while it is vibrating would cause such a change in its frequency. Two possible ways that a wire could change its length is if the bridge pin becomes loose or if the wire digs into the plate. While the movement would be very slight (as little as 1/1000” or less), this would be enough to cause the wire to change in length, and this in turn would cause a different frequency or a false beat. There are methods to file the slight grooves in the plate at what is called the “V” bar. These grooves allow a side-to-side movement of the string, which changes the length of the wire when vibrating. As the name implies, this part of the plate is V shaped and when the wire presses hard against the tip of the V for many years is creates a groove. The movement of the string in this groove can also cause buzzing sounds. Steel wire is harder than the cast iron plate, allowing the wire to make a groove slot along the “V” bar.

When the piano was first built the bridge pins are hammered into drilled out holes in the bridge. The size of these holes was slightly smaller than the size of the bridge pins, thus creating a tight fit. But over time the wooden bridge can dry out and the hole becomes larger, or is worn to the side since the string is pressing firmly against the bridge pin. Whatever the reasons, the string can change in length ever so slightly to allow a different length of wire to vibrate. These variations in length cause a variation in its frequency or a false beat. To make matters even more complex, there are a variety of possibilities when there are 3 vs. 2 wires involved.

Another possibility has to do with the string itself. The making of treble wire is a fascinating topic and beyond this article. But making a string at precise diameters and tensile strengths is difficult, if not impossible. The wire can vary in size even when brand new. But over time, the wire can stretch out unevenly as the tensile strength varies along the wire. It does so because nothing is ever perfect in manufacturing a product. These uneven wire diameters can create false beats. There are tools to help fix this problem by rubbing the wire even, but it is often a hit-or-miss “fix” in my experience.

Finally, there can be false beats due to uneven hammer densities. This can to some degree be addressed with voicing. Voicing is another complex subject, but essentially it involves the breaking up of the tension of the hammer felt to soften the felt. This is done with a voicing tool – a device with different size and length needles that are made to cut into the hammer felt. One can also create a harder felt by filing the hammers down to firmer felts. In short, voicing can help reduce false beats as the hardness of the hammer can cause false beats – at least sometimes. There have also been suggestions that the soundboard itself can produce false beats. There are no adjustments to the soundboard other than replacing it, which is a costly and expensive process. One would not replace the soundboard for voicing reasons alone!

I have had clients who complain that right after I tune the piano it seems to go out of tune almost within a few days or the day of the tuning. There can be many reasons for this and that involve even more articles. It may seem that tuning is just adjusting the tuning pins to set a frequency for each string, but in reality it not that simple! I recently took twice the time to tune a piano that the pianist complained often quickly went out of tune. But after all this extra time and effort there were still many unisons that sounded out of tune or were not as clear as I would have liked. These were all due false beats. I can try to reduce these false beats by tucking them away via blending them carefully into other over tones, but one forte blow would be all it would take to loose this careful blend. Interestingly, I have seen instances where all three strings for a treble note had false beats individually, but when played together the sound was pure. I can only assume that each of these false beats were in the same pattern and thus unable to hear. This is a good example of the many issues that tuners are confronted with all the time. The task of playing the piano has been said to be easy too. Just play the right note, at the right time and the right way. But pianists universally will proclaim that it is not so easy because what is defined as the “right way” requires a lifetime of work. The same applies to tuning a piano!

It is often difficult to help piano teachers find solutions of issues related to offensive tonal issues like false beats. The plain fact of the matter is piano teachers often do not make high incomes to be able to afford these “fixes”. And large jobs, such as restringing the entire piano with new & larger tuning pins and strings, is very expensive. Even taking the tension of the strings down in order to move them to the side to file the V bar or replace the bridge pins with larger pins can take an entire day, not to mention the multiple tunings to bring the tension back to concert pitch; and then tuning over a few weeks to stabilize the tuning. Voicing is possible too, but if the hammers are old and worn, installing new hammers is often the only answer. And whenever hammers are replaced, it is also best to replace the hammer shanks as they take a tremendous amount of abuse from being played 10,000s of times. All this work leads to a full regulation of the action. And all this work adds up!

I hope this article has provided some understanding of this subject. Like so many aspects of the piano it is better seen, heard or explained while at the piano and demonstrated. There are no words that can clearly express what a false beat really sounds like. But if you wish to hear this phenomenon, ask your tuner the next time he or she comes out to tune the piano. They can demonstrate a false beat in person and explain what to listen for so you can experience this phenomenon first hand.Type your paragraph here.

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FAQ's

How Often Should a Piano be Tuned?

This is the question most asked by my customers. I am going to provide three answers and you will see that the answer to this question is a bit more complicated than it appears on the surface. I also am offering a short article that explains in greater detail more about how a piano goes out of tune and more…

The stock answer to this question is to tune the piano twice a year. This is the answer most manufactures provide as a minimum and is based on the idea that after two seasonal changes the piano needs to be re-tuned. Humidity changes created by seasonal changes outside have a major impact on our homes inside. Our DC area winters are very dry with the relative humidity as low as 15% and summer as high as 60%. In short, the reason why pianos to go out of tune more than anything else has to do with changes in humidity. These changes also affect the pitch or overall tension of all the strings in the piano.
The better answer to this question is to tune the piano at every seasonal change or whenever the piano loses more than 3% in over-all pitch. This 3% may seem insignificant to the novice, but the piano tuner knows all too well he cannot pull the overall pitch up more than this amount without consequences. Doing so would cause enough pull back on all the strings so that the tension would fall back unevenly, thus creating a poor tuning in the end.
The last answer is the least known and the most complicated! It takes an in-depth understanding of how all the structural components of the piano interact with each other in what is a very complex manner. These components are by name: the soundboard, bass / tenor / treble bridges, ribs, rim, and plate. In short, the proper tension on all the strings allows the proper relationship of these components to be at their best. When this relationship is preserved over the life of the piano it will last longer, provide the best tone quality and hold a tuning better & longer. To understand this a little better, I often refer to the idea of keeping car tires properly inflated because this is a subject most people have had some experience with. When tires are properly inflated they allow the car to drive better, safer, brake reliably and the tires will last longer and to reach their full mileage warranty.

Conclusion

For most people service is neither exciting nor sexy. It is simply something we all know we must do or we pay the consequences later. Nonetheless we all have a hard time getting motivated to act. We often procrastinate as it is easy to put off, and we like to think that not tuning seemingly has no direct consequences to the piano. As you should have learned by now - this is not true! When the piano is not tuned regularly it not only goes out of tune, but also loses overall tension on all the strings over a period of time. This in turn causes a loss of tone quality, as the proper tension allows for the full array of overtones for any given note. Many music teachers feel it is critical that students play an instrument that is at the proper pitch. More importantly, the loss of proper tension creates uneven stresses on structural components that can cause major problems over many years and reduce the life of the piano. The only way to keep the strings at the proper pitch for each note (or what is commonly referred to as "concert pitch") is by regular tuning. Whether this means a 2 to 4 times a year schedule depends on the piano, it's age, design, quality and the environment of the home. You should consult with your piano tuner to learn more about how your piano is doing and follow the appropriate timetable that works for your situation.

In some instances, adding a humidity control system called the "Dampp Chaser" system inside the piano may be suggested. [This system has recently been re-name the "Life Saver" but it is the same product] This system can only be sold and installed by tuner / technicians. Ask me more about this product when I see you for an appointment. I have a Dampp Chaser brochure and a technical bulletin on humidity control I can provide to you for more information. In short, what this system does is control the humidity level inside in the piano to 43 % R. H. 24/7/365, which is maximal for the piano. I recommend this system in general for all pianos, but particularly in cases where the piano does not seem to be holding to concert pitch even with regular tunings

Why a Piano May Need More Than Just a Tuning?

If and when the strings drop in pitch substantially from the piano not being tuned over a long period of time, an additional tuning is required called a pitch raise tuning. This pitch raise brings the tension of all the strings slightly above concert pitch, which allows for pull back of this added tension. The amount of pull back is carefully calculated by the tuner so that each string will be very close its proper frequency after the pitch raise. But because of the huge load of tension involved in a pitch raise, the tuning is not stable and thus requires a follow up fine-tuning. Tuners often say that "the piano needs to be in tune before it can be tuned". In short, we have to have all the strings within 1- 3 % of the proper frequency before we can attempt to tune a piano. Otherwise, the pull back on the strings will throw out the entire tuning in the end. I usually wait a 1-4 week in between the pitch raise and the regular fine- tuning to allow the piano to fully adjust to the new tension. I find this allows for a more stable final tuning in the long run.

If you have any further questions about this subject please call or talk to me in person when I am at the house to service your piano. This subject can be quite complicated, as you will see if you read the accompanying article. Manufactures and piano dealers have never really addressed this subject because it is a negative. If you do the math, it can cost more to tune & maintain a piano properly over its lifetime than the cost of the piano! This is true for other major items such as cars, homes etc. as maintenance over years is costly. Fortunately this cost is spread out over those years. A small ~$200 a year investment to maintain the piano will keep it is great condition and also allow a technician to check the piano regularly for any other possible issues - issues that when caught early can often avoid major costs in the end.

How Pianos Go Out of Tune and more…

By now you are aware fully that humidity changes cause the piano to go out of tune. But how humidity actually affects the piano and how a piano goes out of tune has not been explained.

The piano is a huge dichotomy in a structural sense. On one hand, the soundboard must be able to freely move to generate sound, but on the other hand it must be extremely stable to hold the 40,000+ pounds of tension on all the strings. In order to allow these two factors to exist together the piano has been built in a precise manner. It has a huge cast iron plate and solid outside rim to contain the tension and a diaphragmatically shaped soundboard to allow for free sound production. The dome shape of the soundboard allows both up bearing and down bearing. Think of this bearing issue as pressure on the soundboard. The up bearing is created when the dome shape of the soundboard is formed in the factory. Its' shape is reinforced by ribs underneath the soundboard to hold the shape in place for many years. The down bearing is created by pressure from the strings crossing over the bridges at a slight angle (1-4 degrees) to the soundboard. This angle is so slight that it cannot be detected by the naked eye. The dome shape of the soundboard cannot be seen either. The down-bearing pressure can be between 1,200 and 1,500 pounds per square inch. At concert pitch the up bearing and down bearing are roughly equal, thus allowing the piano to hold its tune and freely vibrate to create sound.

With this massive set up and diametrically opposing forces, the piano is a dynamic device that sits in front of us with all its this power in a passive state. Most people are unaware of these huge forces, nor the complex structural relationship of components of the piano. Given these forces, tuning the piano involves not just adjusting each string to the correct frequency but also wrestling with these massive forces. The piano tuner knows all too well that one cannot approach tuning without knowing how to approach handling the huge loads of tension in the piano. This brings us to the point where it needs to be understood that over time a piano does not just go "out of tune".

As the humidity increases the soundboard dome increases or expands, and conversely when the humidity drops the soundboard contracts, almost flattening out the soundboard in older pianos. This change in the shape of the soundboard shifts the bridges forward or backwards, which in turn changes the tension on the strings. You have just probably learned for the first time why a piano actually goes out of tune! But if you take this one step further you realize that the tension does not just slightly change (or cause the piano to go out of tune) but can also cause the strings to lose their overall tension to a great degree over a long period of time. When a piano goes out of tune over a 6 month period it generally looses a small amount of tension of somewhere between 1-3% of a half step. A half step is from note to note such as (A to A sharp, A sharp to B, B to C). If the piano is not tuned on a regular schedule, the strings will lose even more than 3 %. I often find pianos that are 25 cents flat (or a quarter tone) flat and even more in severe cases. This all happens silently and without any ability to see or hear these changes, as they are so slight. Over many years the amount of pitch loss can be significant enough that tuning the piano will require multiple tunings in order to bring it in tune and at concert pitch. One cannot load 1000's of pounds of tension without it affecting the soundboard, ribs, bridges and plate on a significant level. As a result, the tuner needs to do an extra tuning called a "pitch raise tuning" where the piano is tuned to a slightly higher pitch than normal to allow for pull back by the strings. In some cases it can take multiple pitch raises if the pitch has dropped dramatically (more than 100% of a pitch), as loading too much tension in one session can impact the structural components adversely.

To wrap this all up, one does not just tune the piano just when it is being used or whenever one feels like it. Tuning must be done on a regular base so the over all tension of the strings will stay at the frequency they are all suppose to be at or concert pitch. The advantages of having the piano at concert pitch are: (1) the fullest quality of sound possible from the piano (2) allow the piano to be able to play with all other musical instruments, radio, CDs etc. (3) allow the piano hold its tune better and for a longer period of time (4) help the student develop an ear for what is in tune and (5) allow the piano to last as long as possible without major structural problems.

The key is to not just to have the piano in tune but tuned at concert pitch - a fact I have overstated by now. Why has this not been explained to the general public? In part, the manufactures and piano dealers do not want to discuss this issue. But more aptly, it is a complex issue not easily explained in a short period of time. Most of time I find people like short, quick answers they can understand right away. This issue is not by its nature a short, easy question to answer. There are so many factors and terms that need to be spelled out first before they all can be pulled together to explain multiple concepts and processes. I even doubt that this short article explains the subject very well. I usually find it best for people to read something like this article first and then have me explain it further in person. I often grab a paper and pencil to help visualize to my clients what is going on in greater detail. Seeing all these components in person can also be very revealing, but this can require taking the piano apart. I do not advise you take your piano apart!I hope this has provided a useful basic understanding about the subject of piano tuning. I realize it can be a bit tedious to read about all the various elements and understand the dynamics that go on inside the piano. There are so many other aspects about piano technology that are unknown to the general public. The field is vast and seems to never have an end. Even after many decades in the field I learn something new at every conference I attend.