"Self tuning piano" questions

[Don A. Gilmore]

----- Original Message ----- 
From: Isaac sur Noos
To: Pianotech
Sent: Wednesday, December 24, 2003 10:12 AM
Subject: RE: "Self tuning piano" questions

>Don, hello, thanks for your proposal to give us some better understanding
of your system.

>First I wonder if the strings have to be heated all day long to stay in
tune. ( a concern about >warmness/dryness in the instrument)
>From a metallurgic point, the strings when heated are less stiff also,
can't it change the spectra significally ( I >have tried to heat strings
rubbing them with a piece of wood, and the change in tone is amazing)

No, the system is only on while you play.  It turns off automatically when
you are finished.  Most people don't understand just how low the
temperatures of the strings will be.  They will be around 95 F (35 C).  The
keys in your pocket are warmer than those strings will be.

>Third, I guess a "master tuning" is recorded in the memory of the system,
and indeed that should be precise >enough in terms of justness for most uses
(-assuming the system can even the pitch reading or be calibrated >at the
end of the ringing time where the string is supposed to be more stable in
pitch) - but what I suspect is >that a system like this can't produce the
most pleasing tone that only good aural tuners are producing . Not >to say
that the system may not be very useful, for instance in Jazz clubs or in
parts of the word where it is >difficult to find a tuner, but the tone
projection and the color of the unisons is something we don't really have
>understood yet I believe.
>As it seem to me that these are very much related to a regulation of the
phase between couples of strings, >and that the tuner try to match well this
phase with the acoustics available,  (hammers, soundboard, strings, >room)
to obtain the very best tone he can, I wonder if you have tried to take
these phase questions under >analysis and try to obtain an acceptable
dealing of those.
>My take is that it is not possible to have 3 strings coupled and phasing to
gether, one being in reverse phase >from the others systematically (if I are
wrong please tell me) Then the second take is that these phases are >playing
a role in the way the strings system loose its energy (so it plays a role in
the way the attack is >stabilized)
>That could be may be a very fine analysis of the pitch - while I guess the
precision needed is not possible >with current equipment - of each string,
if one accept the idea that one of the strings is most probably a tad >lower
or higher than others, I noticed that if one tune 3 strings by plucking
them, with a very precise ETD   >(and an ear check) , the final unison have
chances to be harsh or not carrying well.
>So I am curious to know if you have worked on that part of the analysis,
tuning being considered like >voicing (impedance match between strings/board
stiffness and hammer/action reaction ?

The tuning isn't "produced" by the circuit; it is "recorded".  The strings
are warmed to a median temperature at the factory and then the piano is
properly tuned by hand.  This tuning is stored and then repeated in the
future.  Though each string may be tuned using harmonics, the fundamental
must follow and this is what is stored: the actual pitch of the string.  So
no matter what the temperature or humidity are on a given day, the strings
will brought to this pitch, regardless of the temperature of the string
required.

Each string has its own magnetic pickup coil that detects that, and only
that, string.  They are individually tuned to the exact frequency at which
they were when tuned at the factory.  The method I use for pitch measurement
is accurate to about 1/6000th of a cent at the low end of the piano.

Incidentally, there will also be a "store" feature that will allow an owner
to record someone else's tuning in case they are not pleased with the
factory tuning, or might actually need to have the piano tuned to their
acoustic room conditions.  We also plan to sell a "deluxe" model that can
have alternate tunings available.

>Nowadays we are amazed by your system.
>Another thing I can say about unisons tuning. Before understanding how to
tune nice unisons, most tuners >realize that the piano tones sometimes
better after having played a bit, most probably because some state of
>equilibrium in resonance install itself in the strings system. After having
understood how to tune that part of >the tone from the start, we see that
the tone is only subject to degradation when played, but mostly the >better
stability from the start lend to a more pleasing sound that evolves way
better in time generally (than >the evolving coming from a less full tone to
begin with).
>As usual so intellectual and "artistic" ideas !!! (that is why it is easier
to instruct someone with nice >comparisons than with acoustic facts) The
piano "talks " to you, the tone suddenly "escapes" of the piano, >the piano
"sings" the unison have an "immobile move" ... and so on !
>Congratulations again for your work and thanks to be there on that list - I
also like the way you express >things, some tend to confuse "a bit of salt "
and " a bit of pepper" (not me of course!) .
>With all due respect and best regards.
>Isaac

Thanks for your kind comments, Isaac.

Don A. Gilmore
Mechanical Engineer
Kansas City