More plucking vs. playing

[ricca@nuct.udallas.edu]

Dear Keith,

Okay, I think that I am now in a better position to say something
intelligent about your question. (I'm sorry I didn't know the background
better - I'm new to the list.) I think that I'll try to stick to looking
at the physical aspects of plucking vs. playing.

Although William Braid White is largely correct in his thoughts on the
tone of the piano, research done since his time has shown more about
how the piano actually produces its sound. In particular, there are
two elements which contribute to the tone of the piano which we can
look at separately. The first of these is the hammer, and the second is
the soundboard (and bridge, and how the strings are coupled, etc.)
Naturally, plucking only gives information about the latter. The importance
of the hammer comes largely from the "non-linear" nature of the hammer.
(Essentially, if something is linear, and you hit it twice as hard,
then you get all the same results, just doubled. However, if something
is non-linear, then hitting twice as hard gives things which are not
just doubled; for a hammer this means that the ratio of the amplitudes
of the various partials on the string are changed at different dynamic
levels.) By plucking, you are largely removing any tonal characteristics
which depend on the dynamic level. In addition, you are removing the
tonal influence of the action (which is not negligible in playing).

It seems to me, then, that removing these aspects from the sound that
you hear could help a trained ear identify certain problems and make
certain adjustments more easily; if nothing else, the system being
studied would be a bit simpler. But back to the physical aspects.

One thing which plucking is very likely to do is to reduce the ratio
of the loudness of the prompt sound to after-sound. (Prompt sound, if
you are looking at a single string, comes largely from the vibration
of the string perpendicular to the bridge. After-sound comes from the
vibraion of the string parallel to the bridge. For multiple strings,
things are more complicated, but plucking only one string of a unison
still gives the same result.) Since most of the "sustain" of a piano
is due to after-sound, plucking could be a good way to look at this.
(After-sound must be important: go to a digital piano built a couple
of years ago, and play it. Short notes don't sound too bad; long notes
have, on many models, an organ-like quality to their sustain. This isn't
meant to be a judgement on digital-pianos; just a convenient experiment.)
By looking at the after-sound, you can get an idea as to whether or not
a piano will support certain types of playing: if the sustain isn't
there, then nothing you do to the hammers or action will correct the
problem.

Hope this helps some...

Barney Ricca
ricca@nuct.udallas.edu