Research for fine tuning unisons

[Dan & Martha Reed]

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> Concerning changing (lowering) the pitch of a solid wire by rubbing the
> wire with a brass dowell,
> Dan Jackson wrote...
>  >snip>
>>Have you thought about trying to measure the pitch or the tension
>>change (if any) in the duplex area and between the tuning pins and capo
>>or agraffes? It seems pretty important in order to establish a complete
>>idea of what is happening. Checking the duplex area aurally would be
>>possible but maybe not accurate enough.?
>  >Dan J in Wmbg VA
>
> Dan Jackson,
>      Thanks for your input. I will try some aural tests in these areas you
> mentioned.
     Here are the  findings of my  research so far...
> Today, I played with lowering the pitch of a solid wire by the 'heating'
> method... that is, rubbing the wire with 6 to 8 ten inch strokes, using a
> brass dowell with a rounded groove cut into the tapered end. I am still
> amayzed at how much of a pitch change that 'simply' rubbing the wire causes. I
am
> applying as little downward pressure as possible, so as not to pull the
> wire through its termination points. I am also surprised at how the pitch
> climbs right back up, when the unison is played. It takes about 30 sec. for
> the pitch to come back up, and of course it can be heard coming back to
'about' beatless, as one plays the unison, about 10 times.
>     The theory I am trying to 'prove', with the rubbing method, is that the
> wire will not come up to 100% of it starting pitch, after rubbing. During its
fall, can 100% of the 'loss' be recovered?  There is also a
> possibality, that some wire which has some slight uneveness in the lenth being
> rubbed, and will 'strighten out, and therefore lengthen, and drop in pitch.  I
> say this, because one can feel the bumps in some wire, when using this tool.
>     My test for pitch involves using Maj. thirds (which produce a fast beat
speed) and maj. 6ths., and comparing the beat speeds of two solid
> wires, and then lowering the 'high' wire with the rubbing method. There is the
> temptation to force the wire to pull through its termination points, to cause
> a greater change, because the net effect of rubbing seems to be minimal. (The
more
> aggresive method, that of pulling the wire through its termination points,
> is useful, and more commonly used, but I am limiting this study to what our
> fellow technician Graeme Harvey correctly idenitfied (I beleive) as heat
induced change, by rubbing,
> causing the wire to lengthen slightly( lengthening is my guess).) But, minimal
change is O.K. for some
> unisons, oui? i.e., this method might work well when very small changes are
> useful for nailing a unison. I am looking forward to modifying the stroke
> amount/length of stroke etc., to see if there is a reasonable, predictable
> method that can be used. For now, I have limited the stroke to about one
> half the length of the speaking length of the wire, and have been testing in
the two octaves starting from about middle c - up.
>     The piano I am testing on, is one that gets tuned once a week, (about a
> 30 year old 9' Baldwin) so I have the luxury of spending time trying to
> clean up unisons.

Dan Reed
Dallas Chapter

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