[impedance]

[Don]

Hi Marc,

The tools have only become available *cheaply* recently. I really feel that
RCT is on the fringe of the type of accuracy you are looking for. And
unfortunately voicing atleast *does* physically change the frequencies of
the partials. Voicing is nothing other than changing the dwell time of the
hammer on the string. One way to look at it is that the hammer acts not
only as an exciter--but as a filter at the same time. Of course being made
of felt and wood it is extremely sensitive to humidity changes. Both Mass
and density vary. Then there is the difficulty of striking a key *exactly*
the same way twice. It is sort of like North American TV. It is called
NTST--which is often jokingly translated as Never The Same Twice, in
regards to color balances.

It is also a known that sound boards *do* effect inharmonicity--but to what
extent is unknown at the present time. One of the factors would be
stiffeness which would change with moisture content. And of course by
definition inharmoncity affects the real frequencies of the partials.

We are dealing with a whole truck load of *non linear* responses. It may be
that looking at the *big* picture may more useful that looking at the
*bumps* (i.e. the flea, on the hair, on the frog, on the log in the hole in
the bottom of the sea).

Most of the data that has been collect is suspect but you might look for
the Scientific American article on the coupled motions of piano strings. It
atleast attempts to look at frequency when more than one string is singing.

I don't know if the ratios change or not--but I would not count on them
staying in a linear relationship. I hope I am wrong. Maybe some day you
will be able to enlighten me.

At 10:39 AM 06/14/2000 EDT, you wrote:
>Don:
>
>Clearly, as the humidity and pressure change, the physical size of the
support
>structure changes, as does the coupling of the strings to the soundboard, and
>perhaps bearing angles change at the bridges and agraffes. If the only thing
>that changed were the tension on each string, I'd expect all partials on any
>given string, whether harmonically spaced or not, to be multiplied by the
same
>factor (which could even vary from string to string). This would mean that
the
>*ratios* of higher partial frequencies to the fundamental on each string
would
>remain unchanged. I hear you saying -- not surprisingly -- that the absolute
>frequencies change with weather, rather than the ratios of partial
frequencies
>to their respective fundamentals. If the ratios themselves were to change, I
>would find it very perplexing.
Regards,
Don Rose, B.Mus., A.M.U.S., A.MUS., R.M.T., R.P.T.

Tuner for the Saskatchewan Centre of the Arts

drose@dlcwest.com
http://donrose.htmlplanet.com/

3004 Grant Rd.
REGINA, SK
S4S 5G7
306-352-3620 or 1-888-29t-uner