Re: Plucked strings

["Bernard G. Cleyet & Nancy Ann Seese" <georgeann@REDSHIFT.COM>]

William Beaty wrote:

> On Mon, 3 Jul 2000, David Abineri wrote:
>
> > Am I correct in explaining string instruments, to say that a string
> > actually vibrates in many modes simultaneously when bowed or plucked?
> > That is, is it producing its fundamental along with several harmonics
> > all at the same time?
>
> Yes, but the phase of the various frequencies is important, with the
> --------------- cut

> The hammers inside pianos are made of felt, which would tend to eliminate
> these high-frequency pulses (the felt would "push upon" the string for a
> long-ish time, rather than striking it briefly.)

For those not familiar:  There is a relatively rare (now) percussive, non felted, keyboard instrument, the  clavichord.  The string (sometimes pair of) are hit by a brass tangent (the other end of the
key). The unfretted Clavi. requires that the tangent define the length (pitch) of the strings.  This instrument is considerably more expressive than the only other keyboard of the time (before the
piano -forte or piano), expressive, because amplitude not fixed and bebung (vibrato possible)  The instrument is more susceptible to lowered pitch with time because of the, before playing, low tension
of the string.  The advantage of this instrument is its portability and it is very inexpensive compared to the plucked instrument, the harpsichord.  It is, as one expects, very very soft.  The H. is
usually limited to only two amplitudes (single rank ones) and two timbres.  The buff or lute stop is obtained by pressing a small piece of felt against the strings near one end; no bebung and with
much higher tension (nothing compared to the modern piano), therefore, inaudible pitch change on decay.  The h's plectrum originally used quill, now delrin.  I prefer leather, but requires much more
maintenance.

> Heh.  Ever hear of Franklin's Glass Armonica?  It was an "organ" made from
> slowly rotating glass bowls, played with wetted fingers.  It's one of the
> few instruments which lacks these "plucking harmonics", and people of
> Franklin's time did not know what to make of it's sound.  The first time
> Franklin's wife heard it, she feared she had died.  The device aquired the
> reputation of driving people insane, and both Mozart and Anton Mesmer were
> great fans.  I wonder if the missing "plucking harmonics" made all the
> difference?  http://www.glassharmonica.com/armonica/franklin/

Yes, a flute is usually used instead, very uninteresting timbre, mostly a curiosity.

>

-------cut

>  Maybe the string acts as a nonlinear medium where
> different frequencies travel at different velocities.  If so, maybe the
> pulses become "chirped" into a bunch of short, out-of-phase sine waves
> which make sounds resembling white-noise.

A bowed instrument, when bowed very near the bridge, sounds less "note-y" (as my LA Phil. friend calls narrow band noise), because the fundamental (and lower harmonics?) is suppressed or not excited.

bc

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> William J. Beaty                                  SCIENCE HOBBYIST website
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