R: Unison Flatter than each Individual string?

[Susan Kline]

Luigi -- Your English is excellent, and very clear. Welcome to the list!

Your ideas about coupling throughout the piano sound correct to me. Of
course the effect will be far greater with the dampers off the strings,
or nearly off the strings. No doubt this resonance is what a pianist is
controlling with half-pedalling. The octave stretching would affect this
resonance, but I feel that the fifths-and-fourths clarity is also in
play, which brings us back to temperament questions.

Susan Kline

At 10:44 PM 8/14/2002 +0200, you wrote:
>Just a thought:
>Whenever a string vibrates, it exchanges energy with other parts of the
>piano. During this "mutual" exchanges, the phase may very, and that's what
>the phase display is showing. The variation may be upward, meaning that
>impedance is getting higher, or viceversa downward.
>
>Maybe we should consider not only the coupling between the strings of the
>same unison, but also the coupling with all the other notes, even if with
>the damper down. They are all "damped tuned oscillators", ready to eat (and
>maybe rebounce) some energy from our playing note. To get a more "corporeal"
>idea of what I mean, just put your hand on the bass dampers while you play a
>note in the middle or treble, possibly on a good piano.... and you will feel
>that it's a MUCH MORE COMPLICATED question than just rising a little bit one
>string. This is something which is not under our control, besides the small
>correction we can do on unison. The only way we can change somehing, in his
>sense, is by stretch. I mean, if octaves, or maybe 12th, are more consonant,
>it will be easier for energy to go from our played note to the the other
>strings. If they are somehow further, the transfer will be slower, so the
>decay.
>Sorry I'm not very clear, but I'm not a phisician, nor I speak English.
>Greetings.
>
>Luigi Lamacchia
>Bari - Italy
>
>-----Messaggio originale-----
>Da: owner-pianotech@ptg.org [mailto:owner-pianotech@ptg.org]Per conto di
>Richard Brekne
>Inviato: mercoledì 14 agosto 2002 8.19
>A: pianotech@ptg.org
>Oggetto: Re: Unison Flatter than each Individual string?
>
>
>Hi
>
>baoli liu
>
>I kind of get the feeling that both the soundboards
>vibrational modes as you point out, and also the condition
>of the bridge gets into the picture. How springy or massy
>the impedance characteristics are at the bridge, even before
>the soundboard modes get into the picture may come into
>play. For that matter the condition of the bridge pin
>(whether its tight or loose in the bridge) might play some
>role.
>
>In any case, I cant say that I have been able to observe
>that string coupling results exclusively in pitch drop.
>Actually I am not sure that this pitch drop happens
>significantly more often then other things.
>
>On the side, it seems more and more to me that both pitch
>decay and and whether the pitch rises or falls in coupling
>also have something to do with coincident partials to the
>note being played. I find what looks very much like
>increased sustain especially in the high treble when I use
>the perfect 12ths tuning. And it also seems to be that when
>this "extra" sustain is most apparent, the unison displays a
>slight rise in pitch as as it decays. Weird.
>
>But like I say, I believe the whole subject matter is not
>completely understood, and that like our understanding of
>just how the soundboard vibrates and other such subject
>matter, lots more hard research and experimentation is
>needed.
>
>RicB