Birdcage, more....regarding pitch raises

[Ron Nossaman]

Hi Jay,  'stuff' interspersed.


>I agree with Jim regarding pitch raises.  I've heard the common phrase from
>the client:  "The last tuner said it will take two tunings to bring the
>pitch up to A=440."  I believed this when I first started tuning 5 years
>ago, then read Larry Fine's book, and tried performing full pitch raises on
>one trip with great results -- and continue to do it this way.

* Me too. If the structure will take the tension at all, it will take it all
at once. No guts, no glory.


>Now I find it tricky to know how much I raise the pitch over A=440 in order
>for the pins to settle back to A=440 by the time the pitch raise is
>complete.  Many times it will fall into the correct pitch perfectly, but
>sometimes I run across an old, stubborn upright where the pins stay where I
>bring them up, meaning that I have to lower the pitch after the raise.  And
>then there are the pianos that no matter how high (within safe reasoning) I
>overextend the pitch, it still needs that second pitch raise - I'm finding
>this common on Samicks (but I'm not picking on Samicks).

* Well, first off, it's not (normally) settling pins (or stretching strings,
unless you're doing the first chipping on new strings) that makes the pitch
drop back during a pitch raise. The soundboard is deflecting with the higher
tension and corresponding down bearing load on the bridge. As you tune the
bass and treble, the notes in the middle (that you tuned first) drop in
pitch. How much they drop depends on how much the soundboard deflects with
the increased load. Soundboard deflection with increased bearing load
depends on the stiffness of the soundboard assembly, crown height, crowning
method (compression crowned with flat ribs, or machine crowned ribs), and
string bearing angles along the bridges. That old upright you mentioned
didn't drop in pitch much because the soundboard is probably very nearly
flat (or worse), and the string down bearing angles at the bridges are
probably very low (or non existant) as a result. Increasing tension didn't
appreciably increase the downbearing load on the soundboard, so there was
little deflection, and little resulting pitch drop.   


>Is this procedure common/safe with anyone?  

* Universally common and mostly safe.


>What do you do when guessing how
>much to overextend the pitch for it to fall back to A=440?

* Depends entirely on the individual piano, how it was originally built,
it's present condition, and the whim of the gods. Some people will tell you
to pull above 440 by 25%, 30%, 50%, etc, of how far it was below 440. That's
all great... but. Yamaha grands generally require very little over pull, and
Kimball consoles need YARDS of it, usually twice. The lower in pitch the
piano was when you started, the smaller the overpull percentage will be. You
also need different overpull percentages in different areas of the same
piano, derived from whatever percentage you used for your initial pitch.
It's like most things in this business. The questions are easy, but the
answer(s) for any given question ranges from simple to impossibly
complicated depending on how much you need to know and how deeply you care
to dig into it. Just keep paying attention to what happens when you do
*this*, and what happens when you do *that*, and you will find patterns that
make sense enough to apply to the next one. The tough part is determining
just what the heck it is you are seeing while you're trying to figure all
this out. 

>
>Any feedback is appreciated and thanks in advance!
>
>Jay
>

* I hope this makes enough sense to help. If not, 'ask again later' (Magic
8-ball) and I'll make a stab at clarification.

 Ron