A recent post on PW about Charles Rosen’s views on creating a beautiful sound prompted me to finally write this post about something that I’ve been struggling to put my finger on for a long time.
I have heard it said that the same piano can sound very different in the hands of different pianists. To me that is a self-evident truth. But some people then go on to imply that it is somehow possible for a better pianist to play individual notes in such a way that they sound qualitatively ‘better’ than when played by a less accomplished pianist. The question is how differently can a single note be played, and how do pianists really sound different from each other.
The only controls you have over a single note are how loud it is and how long it lasts for. If you are lucky and you have a half-decent piano, then the timbre of the note also changes depending on how loud the note is played. In other words, if Claudio Arrau (for example) and I were both to play the note A4 on the same piano at exactly the same loudness and hold it for exactly the same length of time, then it would sound exactly the same tonally. It is impossible to stroke the key of that A4 in any other way to make the note sound tonally different at the same loudness and sustain time.
Loudness and timbre depend on the impulse that the hammer applies at the strike point on the string. (Impulse is the force with which the hammer strikes the string and the time interval over which that force is applied.) In all upright and grand actions, the hammer is in free flight over the last 1.5 – 3 mm before it strikes the string because, after let off, it is no longer being mechanically accelerated by the key stroke. (I don’t think the flex in the hammer shank makes a difference once the hammer is in free flight.) The mass of the hammer is constant, which means that Newton’s Second Law of Motion is in effect, and it says that force = mass x acceleration. So with hammer mass constant, acceleration nil, and hammer in free flight, the force applied at the strike point is mass x velocity. I am glossing over some of the physics (in particularly the vectors), but in essence I believe that there is no way of applying ‘body language’ to the way the impulse is applied. Pianos are not pinball machines!
So if I can play any individual note in exactly the same way as Claudio Arrau can, then what, in general makes one pianist sound completely different from another, assuming that both can ‘play the notes’ without error. Here Rosen offers the difference. It is one of balance, that of individual notes in relation to other notes. That balance is both vertical and horizontal.
It is vertical within a chord, where the balance lies in how loud one note is in relation to the others.
It is horizontal, where the balance lies in how loud and long one note is in relation to the others before and after it in time. That balance is strongest within the same rhythmic group, then within the phrase, then within musical sections (e.g., first subject, second subject, development, recapitulation, theme, variations, movements, entire piece).
This intersection of the vertical and the horizontal means that there are an amazingly large number of ways of playing even very short and simple pieces of music. And that’s why it is impossible to play a piece exactly the same way every time. The only way to exactly reproduce a performance is to record the performance on a player piano. And even then it isn’t technically speaking 100% accurate (even though it may sound so to the human ear).
And the difference between me and Claudio Arrau? Apart from the fact that he’s a virtuoso and I’m a keyboard klutz? He does the ‘balancing’ act much better than I do.
Edit: Here is one investigation of the mechanics of tone production. The authors are ambivalent about whether or not the pianist’s touch can influence the tone of a note in any way at all. What is truly amazing is that the hammer/string interface is very complex. It is dependent on the location of the strike point, the mass and length of the string, the flex and vibrational modes of the hammer shank, the compression characteristics of the hammer felt, and the overall mass of the hammer/shank assembly.