Pianotech

I had a kind of "aha!" experience on the week-end, when in working on a number of pianos in preparation for an event, the implications of the idea of a gradient of tone in voicing stood out to me more clearly.  I was working with a 1990 Steinway B, noting how nicely the tone quality progressed from one dynamic level to another, when I realized that I was enjoying precisely what was eluding me on other pianos I have been struggling with in recent days.

In a number of cases, the work that I do in voicing maintenance produces exactly what I want.  Conservative reshaping of the upper shoulders of hammers on several instruments has dialed back the growing stridency in the middle dynamics without taming the forte.  A new set of Abel hammers from Bolduc that I installed in a reworked 1916 Nordheimer are performing well.  In the latter case, I did some needling in the lower shoulders before installation, and did not have to do a whole lot more than that.

On some other instruments, however, I seem to be faced with a simple choice between stridency at all dynamic levels and a lack of power at forte levels.

When dealing with a set of strident hammers that is well into its service life, my first move is to remove material near the strike area, shortening the lengths of the grooves, while seeking to restore something resembling the original curved profile of the crown.  Sometimes this is enough, but sometimes it isn't.  My second move is often to use a single needle, inserting it near or at the end of each string groove, angling away from the center line of the hammer.  I typically do this at both ends of each groove.  If the hammer is particularly resistant to the insertion of the needle, I might first do an insertion just outboard of the end of the string groove first.  This usually gives access to a less strident tone at lower dynamic levels.  However, in a number of instances, the focus of the forte has been lost.

On one occasion I worked to restore the lost power by using a mild solution of B-72 just outboard of the string grooves, but in time this resulted in a return of the strident tone at all dynamic levels.

I do wonder what needs to be modified in my approach, but I also wonder what other factors are contributing to my experience.  Some of these pianos have lost a significant degree of the original impedance of their soundboards.  How does this factor in?  Some have replacement hammers that I regard as being beyond the appropriate weight.  I suspect this plays into the picture as well, though I do understand that there are specific strategies in voicing heavier hammers.

In a few weeks I will be revisiting a Yamaha U1 in a small-town community hall.  Last time I visited it, if I recall correctly, I felt like it was screaming at me, and I did some voicing, probably both reshaping the hammers and doing some needle work.  The response of the users was that the piano lost its ability to speak into the space the way they wanted it to.  I will bring along my B-72, but I'm hoping I can do more than put it back into the strident state in which I found it last time.

I look forward to your comments.  I think I'm poised to learn something.  Thanks for any input you might have.

------------------------------
Floyd Gadd RPT
Regina SK
(306) 502-9103
------------------------------

Floyd,

It is interesting you have observed many impressions of aging pianos as I. There are many aspects to those problems. Aside from the hammer filing you mentioned which could contribute to tonal deterioration including the shorter filed hammer not striking on the proper strike line or not striking at a 90-degree angle there are other possible issues. Issues you have touched upon.

It is common knowledge in the audio business that low frequencies suck up the most energy, i.e. the fundamentals. There is a low frequency in the tonal equation we tend to forget, that being the hammer impact frequency. That frequency is so low it would be equated to one hertz per second or even one hertz per two seconds. In other words, a great amount of low frequency energy is projected in such a short time we tend to dismiss it because we focus our attention on the string fundamental and harmonics. Keep in mind, the piano is a percussion instrument.  As with percussion instruments, the percussive attack is part of the tonal quality that defines a particular instrument. The high pitch attack we hear in chimes or the low frequency attack we hear in kettle drums are part of the qualitative identifier.

With pianos, the low frequency attack power level increasingly dissipates through the sound board as the piano ages. This is caused by the low impedance you identified. This low impedance favors the low impact frequency, and we begin to hear the tonal envelope emanating as a thud when the hammer strikes the string. So much low frequency energy has been drawn down by the soundboard it leaves less and less energy for the rest of the tonal envelope and we identify the piano as having a loss of power and sustain.

That's my guess, being thousands of miles from your pianos.

PS. Sorry I can't give you more encouraging suggestions, but do not despair, on the horizon there may be a way to increase the impedance of a sound board without replacement.

Roger

------------------------------
Roger Gable RPT
Gable Piano
Everett WA
(425) 252-5000
------------------------------

Original Message:
Sent: 3/10/2025 8:55:00 PM
From: Roger Gable
Subject: RE: Chasing the tonal gradient

Floyd,

It is interesting you have observed many impressions of aging pianos as I. There are many aspects to those problems. Aside from the hammer filing you mentioned which could contribute to tonal deterioration including the shorter filed hammer not striking on the proper strike line or not striking at a 90-degree angle there are other possible issues. Issues you have touched upon.

It is common knowledge in the audio business that low frequencies suck up the most energy, i.e. the fundamentals. There is a low frequency in the tonal equation we tend to forget, that being the hammer impact frequency. That frequency is so low it would be equated to one hertz per second or even one hertz per two seconds. In other words, a great amount of low frequency energy is projected in such a short time we tend to dismiss it because we focus our attention on the string fundamental and harmonics. Keep in mind, the piano is a percussion instrument.  As with percussion instruments, the percussive attack is part of the tonal quality that defines a particular instrument. The high pitch attack we hear in chimes or the low frequency attack we hear in kettle drums are part of the qualitative identifier.

With pianos, the low frequency attack power level increasingly dissipates through the sound board as the piano ages. This is caused by the low impedance you identified. This low impedance favors the low impact frequency, and we begin to hear the tonal envelope emanating as a thud when the hammer strikes the string. So much low frequency energy has been drawn down by the soundboard it leaves less and less energy for the rest of the tonal envelope and we identify the piano as having a loss of power and sustain.

That's my guess, being thousands of miles from your pianos.

PS. Sorry I can't give you more encouraging suggestions, but do not despair, on the horizon there may be a way to increase the impedance of a sound board without replacement.

Roger

------------------------------
Roger Gable RPT
Gable Piano
Everett WA
(425) 252-5000
------------------------------

Keith,

You're correct about the riblets. That is a local approach where you may have a "killer octave" (Del Fandrich coined phrase) that needs restoring. The problem is that riblets add too much weight to apply them to the entire soundboard. I believe there may be a way to increase the impedance throughout the soundboard without adding significant weight. 

------------------------------
Roger Gable RPT
Gable Piano
Everett WA
(425) 252-5000
------------------------------

Original Message:
Sent: 03-11-2025 01:04
From: Keith Akins
Subject: Chasing the tonal gradient

RE: "there may be a way to increase soundboard impedance without replacement"

Well, there already is: riblets. (Look it up in Journal archives). 

Maybe there are (or could be developed) other approaches, as well but at least the use of riblets is often productive to improved tone.

Keith Akins, RPT

Piano Technologist

715/775-0022 Mon-Sat 9a-9p

www.akinspianocraft.com

Find me on LinkedIn

Original Message:
Sent: 3/10/2025 8:55:00 PM
From: Roger Gable
Subject: RE: Chasing the tonal gradient

Floyd,

It is interesting you have observed many impressions of aging pianos as I. There are many aspects to those problems. Aside from the hammer filing you mentioned which could contribute to tonal deterioration including the shorter filed hammer not striking on the proper strike line or not striking at a 90-degree angle there are other possible issues. Issues you have touched upon.

It is common knowledge in the audio business that low frequencies suck up the most energy, i.e. the fundamentals. There is a low frequency in the tonal equation we tend to forget, that being the hammer impact frequency. That frequency is so low it would be equated to one hertz per second or even one hertz per two seconds. In other words, a great amount of low frequency energy is projected in such a short time we tend to dismiss it because we focus our attention on the string fundamental and harmonics. Keep in mind, the piano is a percussion instrument.  As with percussion instruments, the percussive attack is part of the tonal quality that defines a particular instrument. The high pitch attack we hear in chimes or the low frequency attack we hear in kettle drums are part of the qualitative identifier.

With pianos, the low frequency attack power level increasingly dissipates through the sound board as the piano ages. This is caused by the low impedance you identified. This low impedance favors the low impact frequency, and we begin to hear the tonal envelope emanating as a thud when the hammer strikes the string. So much low frequency energy has been drawn down by the soundboard it leaves less and less energy for the rest of the tonal envelope and we identify the piano as having a loss of power and sustain.

That's my guess, being thousands of miles from your pianos.

PS. Sorry I can't give you more encouraging suggestions, but do not despair, on the horizon there may be a way to increase the impedance of a sound board without replacement.

Roger

------------------------------
Roger Gable RPT
Gable Piano
Everett WA
(425) 252-5000
------------------------------

Hi Floyd,

I had some success taming harsh sounding worn hammers with a 50% alcohol solution generously applied on top. I guess the theory behind this protocol is that is counters the fibers compaction that developed over time, letting some air between fibers to act as cushion...

Try with a bass note first?

Cheers,

I have benefited greatly from the contributions made by Del Fandrich and Jim Ialeggio to addressing the challenge of lost impedance.  A more recent presentation by Del through Piano Technicians Masterclass featured a strategy for minimizing the addition of mass to the soundboard structure.  I have combined the strategies of Del and Jim on the Nordheimer I mentioned above, and was most pleased with the improvement.

My more immediate concern is how to address the manipulation of hammers in the field in order to achieve a better development of tone across the dynamic range.  I have outlined above what I have tried, together with the roadblocks I have encountered.  

One detail I will add will be that occasionally I encounter what I might describe as divots in the strike zone, such that I can reduce the length of the grooves to a more acceptable length, but find myself looking at a surface that is concave in one dimension.  I'm reluctant to remove so much material that I eliminate the existing grooves all together, but wonder if what I am looking at represents a compromise to the hammer-string interface that contributes to the roadblocks I am facing.

------------------------------
Floyd Gadd RPT
Regina SK
(306) 502-9103
------------------------------

Original Message:
Sent: 03-11-2025 08:09
From: Nicolas Lessard
Subject: Chasing the tonal gradient

Hi Floyd,

I had some success taming harsh sounding worn hammers with a 50% alcohol solution generously applied on top. I guess the theory behind this protocol is that is counters the fibers compaction that developed over time, letting some air between fibers to act as cushion...

Try with a bass note first?

Cheers,

The reality is that it's always an interaction between hammer and soundboard impedance and both change over time.  Hammers wear, get less resilient, develop different compression/decompression characteristics and all that affects how they deliver energy to the string and how they rebound off the string affecting both timbre and, to some degree, the filtering properties that are especially important in the treble section.

Soundboards do change impedance characteristics throughout their life and even with humidity cycles.  Riblets won't be a perfect substitute for lost crown or lower impedance because the spring-like qualities that allow the board to stiffen under compression to achieve the requisite level are only part of the story. The potential energy stored in this soundboard spring that is under a certain amount of compression is not the same as adding stiffness by effectively beefing up the rib scale. It might help, in some cases, but it's not a substitute for a fully crowned board that is compressed.  

That means that not only are hammer selections critical in the initial phase of the piano's life but that choice that might have been right then may not be right now that the board has aged. Often that can be dealt with through judicious voicing procedures but sometimes the changes in the hammer and soundboard that occur with age are going in the same direction, less liveliness, less spring, however you want to call it, and those things can't be physically restored.  

At a certain point in a piano soundboard's life, the choice of hammer, and opting for a new, more suitable hammer, is probably the best route. Generally, with lower impedance you will want somewhat softer and somewhat lighter and more resilient (springy), to mitigate the percussive nature of the changing SB and to get the hammer off the string faster to reduce filtering and help, to some degree with sustain, or at least sustain perception.  

As to what specific treatment needs to be applied to aging hammers short of replacing them, it will depend a lot one what the hammer is, what's been done to it already, and how much life it has left in it.  While we can always make things better, sometimes better will not be enough. Shape is critical and affects hammer string contact time and filtering.  But as we reshape the hammer from wear, the hammer dimensions have also been reduced--there is less felt over the molding.  Sometimes that can be a benefit if there was too much there to begin with.  That's often the case with Steinway factory hammers, certainly from previous decades.  But sometimes there will be compromise in the shock absorber nature of hammers with that reduction and that's hard to mitigate. If weight is reduced to the detriment of power, especially in the lower end of the piano, that can be added back easily using mini binder clips or even lead insertions into the molding.  But usually, a lighter hammer will benefit an aging soundboard somewhat.  Building back in the shock absorber by needling high or low shoulder certainly helps but becomes shorter and shorter lived the more the hammer dimensions are reduced.

It should be kept in mind that everything we do in the voicing procedure is destructive to the integrity the hammer.  Either we're adding chemicals that destroy the felt's natural resilience, or we are needling the felt and reducing the tension in the hammer by stretching the fibers apart.  That has benefits in terms of reducing the level of stiffness in the hammer when it is too "hard", but we can't un-needle a hammer to restore tension if we decide we need it back. 

So, at a certain point we may have to cut our losses and rethink what needs to be there based on the characteristics of the existing SB and make the best choice possible when it comes to replacing them.  Long answer to the question of what are best practices, but I think there is no simple answer or general protocol that can address every situation, unfortunately.   

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

My approach when doing this kind of "major maintenance" voicing is to repeat what I have done earlier when "pre-voicing": deep needle the shoulders in a pattern that follows the grain of the felt fibers to the degree possible, opening them up, as opposed to inserting needles at right angles through the layers. The tip of the needle is placed on the surface of the hammer, then pressed in, as opposed to stabbing. This results in far less tearing of fibers compared to creation of springy cushion, by pulling the fibers apart and allowing the natural crimp to be released. I follow a pattern that rotates around the shoulders, leaving a sharpish point of untouched felt just above the tip of the molding. 

I will have filed the hammers in the interim, so the re-needling process will be penetrating deeper into the core of the hammers.

I have found that this treatment consistently maintains a wide tonal gradient, increasing upper partial mix with increased force of blow, and restoring the lower end of the spectrum when playing pianissimo. See attached photo for needle pattern.

------------------------------
Fred Sturm
University of New Mexico
fssturm@unm.edu
http://fredsturm.net
http://www.artoftuning.com
"We either make ourselves happy or miserable. The amount of work is the same." - Carlos Casteneda
------------------------------

Original Message:
Sent: 03-12-2025 15:06
From: David Love
Subject: Chasing the tonal gradient

The reality is that it's always an interaction between hammer and soundboard impedance and both change over time.  Hammers wear, get less resilient, develop different compression/decompression characteristics and all that affects how they deliver energy to the string and how they rebound off the string affecting both timbre and, to some degree, the filtering properties that are especially important in the treble section.

Soundboards do change impedance characteristics throughout their life and even with humidity cycles.  Riblets won't be a perfect substitute for lost crown or lower impedance because the spring-like qualities that allow the board to stiffen under compression to achieve the requisite level are only part of the story. The potential energy stored in this soundboard spring that is under a certain amount of compression is not the same as adding stiffness by effectively beefing up the rib scale. It might help, in some cases, but it's not a substitute for a fully crowned board that is compressed.  

That means that not only are hammer selections critical in the initial phase of the piano's life but that choice that might have been right then may not be right now that the board has aged. Often that can be dealt with through judicious voicing procedures but sometimes the changes in the hammer and soundboard that occur with age are going in the same direction, less liveliness, less spring, however you want to call it, and those things can't be physically restored.  

At a certain point in a piano soundboard's life, the choice of hammer, and opting for a new, more suitable hammer, is probably the best route. Generally, with lower impedance you will want somewhat softer and somewhat lighter and more resilient (springy), to mitigate the percussive nature of the changing SB and to get the hammer off the string faster to reduce filtering and help, to some degree with sustain, or at least sustain perception.  

As to what specific treatment needs to be applied to aging hammers short of replacing them, it will depend a lot one what the hammer is, what's been done to it already, and how much life it has left in it.  While we can always make things better, sometimes better will not be enough. Shape is critical and affects hammer string contact time and filtering.  But as we reshape the hammer from wear, the hammer dimensions have also been reduced--there is less felt over the molding.  Sometimes that can be a benefit if there was too much there to begin with.  That's often the case with Steinway factory hammers, certainly from previous decades.  But sometimes there will be compromise in the shock absorber nature of hammers with that reduction and that's hard to mitigate. If weight is reduced to the detriment of power, especially in the lower end of the piano, that can be added back easily using mini binder clips or even lead insertions into the molding.  But usually, a lighter hammer will benefit an aging soundboard somewhat.  Building back in the shock absorber by needling high or low shoulder certainly helps but becomes shorter and shorter lived the more the hammer dimensions are reduced.

It should be kept in mind that everything we do in the voicing procedure is destructive to the integrity the hammer.  Either we're adding chemicals that destroy the felt's natural resilience, or we are needling the felt and reducing the tension in the hammer by stretching the fibers apart.  That has benefits in terms of reducing the level of stiffness in the hammer when it is too "hard", but we can't un-needle a hammer to restore tension if we decide we need it back. 

So, at a certain point we may have to cut our losses and rethink what needs to be there based on the characteristics of the existing SB and make the best choice possible when it comes to replacing them.  Long answer to the question of what are best practices, but I think there is no simple answer or general protocol that can address every situation, unfortunately.   

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

I will also comment that one can "voice up" a hammer by inserting needles into the core, which releases the crimp/spring of the fibers there so that they will press outward against the tension of the surface fibers. This is most conveniently done using a side needling tool, either the Bolduc style (one set of needles penetrating halfway), where you will need to do insertions from both sides, or using the Jahn tools with needles penetrating from both directions at once. Pricey, but immense time savers if you need to do this kind of thing. Inserting needles this way "by hand" is troublesome as you need to support the hammer laterally, and pulling the needles out can be quite challenging. The springs of the Bolduc and Jahn tools pull the needles back ou with ease.

Another approach is to insert from the lower shoulder just above the staple, angling upward toward the core. This is easier from the back side of the hammer, but can be done from the front (where the shank is in the way) using the Jahn tool made for uprights, the brass tool with the curves. You need to use rather long needles, at least 6 - 8 mm, to get good results.

This is also premised on the shoulders not having been damaged by a lot of stab voicing aiming directly toward the core of the hammer. 

------------------------------
Fred Sturm
University of New Mexico
fssturm@unm.edu
http://fredsturm.net
http://www.artoftuning.com
"We either make ourselves happy or miserable. The amount of work is the same." - Carlos Casteneda
------------------------------

Original Message:
Sent: 03-16-2025 17:49
From: Fred Sturm
Subject: Chasing the tonal gradient

My approach when doing this kind of "major maintenance" voicing is to repeat what I have done earlier when "pre-voicing": deep needle the shoulders in a pattern that follows the grain of the felt fibers to the degree possible, opening them up, as opposed to inserting needles at right angles through the layers. The tip of the needle is placed on the surface of the hammer, then pressed in, as opposed to stabbing. This results in far less tearing of fibers compared to creation of springy cushion, by pulling the fibers apart and allowing the natural crimp to be released. I follow a pattern that rotates around the shoulders, leaving a sharpish point of untouched felt just above the tip of the molding. 

I will have filed the hammers in the interim, so the re-needling process will be penetrating deeper into the core of the hammers.

I have found that this treatment consistently maintains a wide tonal gradient, increasing upper partial mix with increased force of blow, and restoring the lower end of the spectrum when playing pianissimo. See attached photo for needle pattern.

------------------------------
Fred Sturm
University of New Mexico
fssturm@unm.edu
http://fredsturm.net
http://www.artoftuning.com
"We either make ourselves happy or miserable. The amount of work is the same." - Carlos Casteneda
------------------------------


Original Message:
Sent: 03-12-2025 15:06
From: David Love
Subject: Chasing the tonal gradient

The reality is that it's always an interaction between hammer and soundboard impedance and both change over time.  Hammers wear, get less resilient, develop different compression/decompression characteristics and all that affects how they deliver energy to the string and how they rebound off the string affecting both timbre and, to some degree, the filtering properties that are especially important in the treble section.

Soundboards do change impedance characteristics throughout their life and even with humidity cycles.  Riblets won't be a perfect substitute for lost crown or lower impedance because the spring-like qualities that allow the board to stiffen under compression to achieve the requisite level are only part of the story. The potential energy stored in this soundboard spring that is under a certain amount of compression is not the same as adding stiffness by effectively beefing up the rib scale. It might help, in some cases, but it's not a substitute for a fully crowned board that is compressed.  

That means that not only are hammer selections critical in the initial phase of the piano's life but that choice that might have been right then may not be right now that the board has aged. Often that can be dealt with through judicious voicing procedures but sometimes the changes in the hammer and soundboard that occur with age are going in the same direction, less liveliness, less spring, however you want to call it, and those things can't be physically restored.  

At a certain point in a piano soundboard's life, the choice of hammer, and opting for a new, more suitable hammer, is probably the best route. Generally, with lower impedance you will want somewhat softer and somewhat lighter and more resilient (springy), to mitigate the percussive nature of the changing SB and to get the hammer off the string faster to reduce filtering and help, to some degree with sustain, or at least sustain perception.  

As to what specific treatment needs to be applied to aging hammers short of replacing them, it will depend a lot one what the hammer is, what's been done to it already, and how much life it has left in it.  While we can always make things better, sometimes better will not be enough. Shape is critical and affects hammer string contact time and filtering.  But as we reshape the hammer from wear, the hammer dimensions have also been reduced--there is less felt over the molding.  Sometimes that can be a benefit if there was too much there to begin with.  That's often the case with Steinway factory hammers, certainly from previous decades.  But sometimes there will be compromise in the shock absorber nature of hammers with that reduction and that's hard to mitigate. If weight is reduced to the detriment of power, especially in the lower end of the piano, that can be added back easily using mini binder clips or even lead insertions into the molding.  But usually, a lighter hammer will benefit an aging soundboard somewhat.  Building back in the shock absorber by needling high or low shoulder certainly helps but becomes shorter and shorter lived the more the hammer dimensions are reduced.

It should be kept in mind that everything we do in the voicing procedure is destructive to the integrity the hammer.  Either we're adding chemicals that destroy the felt's natural resilience, or we are needling the felt and reducing the tension in the hammer by stretching the fibers apart.  That has benefits in terms of reducing the level of stiffness in the hammer when it is too "hard", but we can't un-needle a hammer to restore tension if we decide we need it back. 

So, at a certain point we may have to cut our losses and rethink what needs to be there based on the characteristics of the existing SB and make the best choice possible when it comes to replacing them.  Long answer to the question of what are best practices, but I think there is no simple answer or general protocol that can address every situation, unfortunately.   

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320