Article on Touch and Tone from EPTA India: A detailed survey on sound production

Piano tone and the pianist’s touch: Prabhudas Ivanson

Although the debate on piano tone as related to the pianist’s touch began almost concurrently since the infancy of the piano, the controversy on the subject intensified and culminated only in the twentieth century.

1. The great scientist Helmholtz in his epoch-making “On the sensations of tone” proved that tone quality or timbre is determined by the relative proportion of the fundamental tone and its various overtones.  He was also the first to explain the interaction between the hammer and the string on the piano.  He states that “In pianoforte playing the effect of the tone-excitation by means of the hammer depends on the length of time the latter remains lying on the string.  For if the soft elastic surface of the hammer is brought against the string without audible blow, then the movement has time to propagate itself before the hammer springs back, and increases gradually and constantly during the time of contact”.

2. The distinguished English pianist, composer and pedagogue Tobias Matthay exerted great influence on piano teaching of the future. In his book “The Act of Touch” he went to great lengths to support his ideas.  His main formulation was that the keys, when brought down “suddenly” gave a brilliant tone, and when depressed “gradually” gave a mellow tone.  He has appropriated Helmholtz’s above quoted explanation of the interaction between hammer and string, to that between finger and key to “prove” his point.  

Josef Lhevinne in his book published in 1924, “Basic Principles in Pianoforte Playing” takes a similar approach to Matthay.  Lhevinne  states: “It is almost an axiom to say that the smaller the surface of the first joint of the finger touching the key, the harder and blunter the tone; the larger the surface, the more ringing and singing the tone”.  Similar sentiments are expressed by Dame Fanny Waterman in her book published in 1983, “On Piano Teaching and Performing”.  

Matthay’s theories were unfortunately often expressed in his writings in an overly complex manner.  Much of his text in his most famous book ‘The Art of Touch’  is extremely difficult to understand.  Matthay’s writings were questioned by one of his pupils, James Ching.  Ching  conducted experiments in conjunction with professors of physiology and mechanics of the University of London which scientifically appeared to contradict  much of what Matthay’s book  “The Act of Touch” seems to suggest.   

3. In a paper published in the British acoustics journal “Acoustics Letters” in June 1984, I had analysed piano tone in terms of any sound whatsoever. Any sound can be analysed as a component of the following five determinants: 1. Pitch, 2. Volume, 3. Timbre, 4. Duration, and 5. Morphology (how the sound begins, goes on and dies away).  

Considering each of these factors in connection with piano tone,

1. Pitch is fixed on the pianoforte.  

2. Volume is proportional to the velocity imparted to the key by the performer, with its consequent striking force of the hammer on the string.  

(It would be expedient to consider 3. Timbre and 5. Morphology together, as they form an integral part of the long-ranging controversy on the problem of piano tone as related to the pianist’s touch).  

Duration is the time lapsing between the beginning and end of each tone, and depends on how long the key is held down by the performer.  

Timbre is the overtone structure of tone (the proportionate strengths of the fundamental tone and its various overtones).  If we consider just the tone from the vibrating string, timbre is solely dependent on the velocity imparted to the key by the performer at the point of escapement of the hammer.  This can be inferred through theoretical physics as follows:

Any moving body has three properties: its mass, direction of motion and speed. As the direction of motion of the piano hammer is predetermined, speed is the only variable factor under control.  Thus, as far as tone from the piano string is concerned, the only factor under the performer’s control is the velocity of the hammer at the instant it strikes the string.  This corresponds to the velocity imparted to the key by the performer at the instant it releases the hammer.  Since the hammer can possess only one speed at any one instant, the manner in which this speed has been previously attained has no bearing whatsoever on the outcome of the string’s vibration and the resultant tone.  

Here it would be apt to clear a misunderstanding. If the key is depressed very slowly, it will take the hammer up like a lever till the escapement point, after which it will tend to throw up the hammer (the escapement point being the point at which the hopper slides from under the roller attached to the underside of the hammer shank, thus releasing the hammer from the rest of the mechanism before it strikes the string).  However, in practice it does not always happen that the hammer is taken up to the escapement point by the key like a lever; due to the initial strike force, the key, in most cases, catapults the hammer against the string before the escapement point is reached.  The inference is that, thanks to the escapement action, the key invariably releases the hammer at the escapement point or some point before it, never maintaining contact with the hammer beyond the escapement point. 

The reasoning through theoretical physics that the tone from the vibrating string is entirely dependent on the velocity of the hammer the moment it is released by the key was experimentally verified by Hart, Fuller and Lusby of the University of Pennsylvania, reported in the “Journal of the Acoustical Society of America” of October 1934, Vol. 6, under the heading “A Precision Study of Piano Touch and Tone”.  A mechanical striker was used to strike the key in a great variety of known and accurately controlled ways imitative of different methods of touch, and the resultant sound-curves were recorded.  These showed that identical volumes invariably produced identical patterns of string vibration, no matter in what way the key was depressed.  With this experiment it was conclusively proved that varieties in manipulation of the key in no way affect the quality of tone from the string – and that the only criterion as far as string vibration is concerned is the force with which the hammer strikes the string/s.  Thus, all the shades of tone which the pianist can get out of the strings of one note form one linear sequence only – this corresponding to the different speeds at which the hammer strikes the strings, which is directly proportionate to the velocity of the key at the instant the hammer loses contact with it, and which determines the volume of tone.

(The experiments also showed the very great differences in quality which are associated with differences in loudness, the higher partials being much stronger in the case of the fortissimo note.  A difference of quality was also found between bass and treble notes when struck with the same force, the fundamental being relatively much weaker in the bass).  

It should however be noted that if the key is struck with absolutely immense force and the velocity of the key exceeds a certain maximum limit suitable for a particular instrument, the string/s struck will vibrate not only transversely, which is the normal manner of vibration, but also longitudinally.  The longitudinal vibrations produce undesirable high harmonics of considerable intensity, resulting in a harsh jangle of sound (if not damage to the instrument itself).  

4. The American investigator Otto Ortmann did extensive research on the

subject of piano touch and tone, and in his book “The Physical Basis of Piano Touch and Tone” which appeared in 1925, he concurred with the view that quality of tone from the vibrating string is solely dependent on volume.  He, however, made the breakthrough observation that various non-musical sounds accompanying the manipulation of the keys added the noise element to the string’s vibration, and classified four such extraneous sounds:

1. The sound made (in all percussive touches) by the finger tip coming into contact with the key

2. The sound made by the key coming into contact with the key-bed

3. The percussive sound made by the hammer coming into contact with the string (as distinct from the musical tone from the vibrating string)

4. Miscellaneous sounds resulting from the various moving parts of the pianoforte action

Ortmann distinguished between the first two of these as being to some

extent controllable in degree according to the touch of the performer, and the second two as being for all practical purposes constant for any given quantity of tone (i.e. uncontrollable in degree by the performer).  Thus a tone of any given quantity can be produced either by a percussive or non-percussive touch.  In the case of the former there would always be some noise made by the finger tip as it comes into contact with the surface level of the key, a noise which would be absent in non-percussive touches.  He argued that this noise might conceivably blend itself with the musical tone from the vibrating string and thereby affect its quality.  In the same way Ortmann argued that the amount of noise produced by the impact of the key against the key-bed can be varied, for a tone of any given quantity, according to the depth or shallowness of the pianist’s touch.  At the same time it was obvious that for a tone of any given degree of loudness the noise made by the hammer hitting the string would always be the same irrespective of the touch form used or the method of key manipulation.

Ortmann left out the fourth noise element as a variable factor, because he failed to take into account the action of the release of the key from its depressed position.  This will be evident if we hold down a whole lot of notes silently using both the forearms, and then let them off suddenly – when there will be an ensuing rattle.  If the same thing is repeated a second time by letting up the keys gently and gradually, the earlier considerable noise won’t be there.  This variation in the mode of release of the key from its depressed position has hitherto been greatly ignored by theorists and investigators on piano touch and tone.  

In the chapter “Tone Quality: Facts and Fallacies” in his book “Piano Playing”, James Ching very interestingly discusses the controversy on piano touch in relation to piano tone.  After Ortmann declared that the extraneous noises of the finger contacting the key and the key contacting the key-bed could blend with the string tone, the pianist no longer attempted to produce any particular kind of key acceleration or deceleration, but focussed on controlling quantity and the extraneous non-musical noises of touch.  However,there are those who also cite possibilities that can arise through vibrations of the hammer shank.  Though such vibrations exist theoretically, I believe that they actually  have no practical bearing on the overall tone quality. 

Ching continues in his book: “The practical position after Ortmann was, therefore, that the pianist no longer attempted, for the control of quality, to produce any particular kind of key acceleration.  Instead, he concentrated on the control of quantity plus the control of the extraneous non-musical noises of touch.  And there the position remained until, in 1938 or early in 1939, Sir James Jeans, that eminent scientist–musician, put the cat amongst the pigeons by maintaining that variations of quality of tone were absolutely impossible in the absence of variations of quantity.  By this statement he implied that he considered even Ortmann’s theories pandered too much to the pianist’s capacity for self-deception. I remember that he made, at a meeting of musicians, a remark to the effect that it didn’t matter whether the piano was played by the pianist’s finger tips or the tip of an umbrella.  

“In a subsequent letter to myself, Sir James explained fully his theory and his reasons for holding it.  There could be no doubt, he maintained, that quality of tone could not depend, as Matthay had always insisted, on the manner of key acceleration.  The quality of the sound from the vibrating string was entirely dependent on the quantity, irrespective of the way in which the key was depressed.  As for Ortmann’s theories, he agreed that the extraneous, non-musical sounds would theoretically affect the quality of the total sound.  But, and this was the vital point, the differences in quality caused by differences in the kind or the degree of the extraneous noises for any given quantity of tone could never be sufficiently great for the human ear to detect them.  Sir James gave me a scientific proof of this point from the science of acoustics and the physiology of the human ear”.  

5. Here again, the theoretical conclusion that the noise of the finger

impacting the key, and the key impacting the key-bed blends with the vibration of the string to produce a difference in the overall tone has been experimentally proved by comparatively very recent scientific experiments. In Issue 112 of EPTA’s Piano Journal, Miha Haas, the author of the second of a two-part article “Tone Colours on the Piano: Acoustic Predisposition or Contextual Illusion” presents the results of the very important experiment by Goebl, Bresin and Galembo reported in their book “Once Again: The Perception of  Piano Touch and Tone.  Can Touch Audibly Change Piano Sound Independent of Intensity?”  which conclusively proves that different kinds of touch can AUDIBLY alter the  initial impact noises.  

It should be clearly realised that while talking of “quality of tone”, the extraneous noises accompanying the timbre of the steady state of tone, which in the case of the piano is the vibrating string, should be taken into consideration as an integral part of the overall tone as perceived by the ear. I here quote from my article published almost concurrently in three British journals around the year 2000: “The duration and type of transient sounds are very important for the recognition of musical instruments, since our ability to recognise different instruments is not dependent solely on the particular timbre or harmonic content.  Thus in a certain part of their  range the steady tones of the violin and the oboe are practically indistinguishable, but they have different ‘starting noises’, due to the action of the bow and the reed respectively, which lend them their distinctive hues.  Further, if a recording is made of notes from a violin, oboe and piano, and a small fraction of the beginning of each note is cut out so that the ‘attack’ is removed, it becomes very difficult to tell one instrument from another”.  

Thus, while talking of tone quality on the piano, it is imperative to take into consideration, along with the harmonic content of the tone from the vibrating string/s, the extra noises associated with the ‘attack’ – the noise of the finger contacting the key and the key contacting the key-bed – which has now been experimentally proved to be audibly variable depending on the touch of the pianist.  

It is now very obvious that the problem of how a pianist affects touch is far more complex than physicists thought it was, early in the 20th century or previous to that.  

It is to Tobias Matthay’s credit that though he gave overly verbose explanations over tone and touch in his writings– he steadfastly held on to his beliefs that tonal differentiations could be obtained on the piano apart from mere volume.  He accepted the limitations of his understanding as the following quote makes clear:  “As this part of the problem – the acoustical explanation of the effects we hear – still awaits final solution, we can here only rely on hypothesis and surmise, instead of upon fully ascertained facts…….Many facts may in the end be found to contribute to the ultimate explanation here still needed”.  

James Ching also acknowledges in his “Piano Playing” that “The available scientific knowledge about any subject is rarely static.  At best we can say that every new piece of scientific knowledge tends to bring us a little nearer to the complete truth about things.  And it certainly seems unlikely that, in connection with the science of piano technique the last word has already been said by anyone”.  

6. Now the final stage in the piano touch process has been reached.  This

 is the manner of release of the key from its depressed position after its due duration.

We may distinguish between the “prompt” and “aftersound” of piano tone, which are, respectively, the initial tone once the hammer strikers the string, and the continually diminishing tone after it has been made. 

Gabriel Weinreich has investigated the variation in decay of coupled piano strings (Journal of the Acoustical Society of America, Dec. 1977, Vol. 62, No. 6).  This refers to how the tone decays after the “prompt” (which is the initial tone when the hammer strikes the string) till the moment of key release (i.e. as long as the key is held down). He has demonstrated how, due to multiple (double and triple) stringing in all but the lowest few notes of the piano, the decay rate of the aftersound starts high and diminishes, and the conclusion reached that the initial decay rate is several times greater than the final decay rate – i.e., the tone diminishes rapidly once it has been sounded, and then lingers on longer without too much dissipation.

The most important factor left out by theorists, investigators and experimenters, is that the tone could be controlled from the point of the depressed key up to its ascent to the surface level, depending on whether the key is brought up abruptly, or in various degrees of graduality as it rises to the surface.  This corresponds to whether the damper contacts the string abruptly or gradually till it is silenced.  

There is vague reference about this in some books (including Ortmann’s), but the significance of the variable graduality of the release of key from its depressed position as it rises to its surface level has never been fully realised. The next major contribution to the subject of piano touch and tone after Ortmann is by Arnold Schultz.  In his book “The Riddle of the Pianist’s Finger” he has commented that “I could not have written my book at all but for the fact that Ortmann had first written his”.  He however states in his book that “a damper either stops the string or it doesn’t”, implicitly denying the possibility of gradations in the release of key, causing either an abrupt or gradual mode of damper contact with the string as it silences the tone.  (The graduality of the damper contacting the string can be controlled even more than the key by the right, or Sustaining pedal being brought up gradually after being depressed).  

In my articles published in the British acoustics journal “Acoustics Letters” of Feb. 2000 and “Piano Journal” of Spring 2000, I had put forward two means of studying the release rate of the keys:      

1. Mechanically with a system which measured the key displacement as a function of time.  

2. Acoustically by measuring the envelope of the vibration of the string.

(It would be interesting to note that I had remarked in the Readers’ Forum

 of Piano Journal, Winter 2000 issue – following the publication of my article in the Spring 2000 issue – that “Matthay’s empirical formulae could have saved so much bother had he, instead of propounding “downward acceleration”, realised that it was in fact the exact opposite – “upward deceleration” – that was required”).  

From all that has been presented in this article, it could be concluded that a comparative study of the release rate of the keys with a group of competent professional pianists will put all the pieces of the puzzle together, complete with fully corroborative experimental scientific evidence, thus bringing about a new rapprochement between the artistic and scientific points of view.