coupled motions

[Don]

At 07:08 PM 11/7/98 -0600, you wrote:
>At last, something technical. This is interesting. I've often wondered what
>I was actually getting away with in tuning unisons. How far into the tone
>did you tune? Were you giving it a second for the attack to coalesce, or
>hitting the key quickly and continuously as you tuned? 

I tuned the note with an impact technic using a *swinger* style hammer. The
blow necessary to get stability was about mf (oh for a sound pressure
meter). The note was beat free to my ears for about 12 seconds (which is
all the jam the piano had to offer). I chose the note because each of the
wires seemed *clean* to my ear--there were no little *extras* as there are
in so many pianos.

The measurements were taken by setting RCT into listening mode and then
striking the note at a p or at most mp level, so they would have the impact
distortion as part of the measurement. I did a similar test last January
where I chose a different note (on the same piano as it happens) and
measured immediately, then at 1 second, and etc. Have a look in the
archives. I keep hoping someone else will try to duplicate the these
experiments--but so far only Gentelman Jim has ever bothered.

After all the measurements the note was still beat free to my ears. 

>I'm thinking that
>after the first half second or so of the attack, the note gets cleaner as
>everything pulls together. I have found that attack distortion lessens as
>the unison is better tuned, so I get better unison tuning in the attack,
>than I do in the decay. Did you try it the other way and tune each
>individual string as perfectly as possible with the RCT, muting the others,
>and measure the pitch of the resulting unison?
no

>
>I'm also curious as to what factors determine how much tuning divergence
>will pull together to an 'acceptable' level. String termination and the
>impedance of the bridge/soundboard assembly would surely affect this, as
>would the frequency, I would think.

I am sure they do affect it--but I am not sure how or which way.

>You probably have a tentative hypothesis
>about what you've got so far, so what do you think?

Tentatively I think I probably listen to the higher partials when I set
unisons. It would be great to dig out my old accutuner and *force* a unison
using the filter output and headphones to *fool* my ears and then measure
the results.

That is the reason I presented the raw data to the list. I hope to do the
same test on a rather old Steinway D (last restrung in 1976).

Regards,
Don Rose, B.Mus., A.M.U.S., A.MUS., R.M.T., R.P.T.
"Tuner for the Centre of the Arts"
drose@dlcwest.com
http://www.dlcwest.com/~drose/
3004 Grant Rd.
REGINA, SK
S4S 5G7
306-352-3620 or 1-888-29t-uner