[pianotech] Pitch raising limit

[Terry Farrell]

I've hear rumors that you are a VT owner. Yes?

Terry Farrell

On Aug 5, 2009, at 10:40 PM, John Formsma wrote:

> On Wed, Aug 5, 2009 at 5:23 PM, PianoForteTechnologies <pianofortetechnology at saol.com 
> > wrote:
> I am at the moment only an aural tuner, due to etd’s being extremely  
> expensive for a South African with regards to the exchange rate, but  
> that’s my problem, could you explain in aural terminology and could  
> you explain at what point the strings become overstretched?  How  
> many semitones can one overpull without the strings being  
> overstretched?
>
>
> The "standard" answer for how much overpull is about 30% in the  
> midrange, 20-25% in the bass, and 33% in the treble, but tapering  
> down to 25-30% in the topmost notes.
>
> A 200 cent pitch raise to A442?  You can't safely use a 30% overpull  
> in this case as that would be 60 cents above pitch.  So, set A4  
> about 20 cents above your pitch source for your first pass. If  
> you're using a a fork, that would be about 5 beats per second sharp  
> of the fork.
>
> However, you should first determine if the piano is structurally  
> sound before doing the pitch raise. For this reason, many tuners  
> would start by tuning A4 to A442 (not going higher than that) on the  
> first pass. By the time you finish, you'll know if strings will  
> break, or if the plate has cracked. <slight grin>  Seriously, you  
> might be dealing with a piano that can't be tuned at A442 for  
> various reasons: wasn't designed to be tuned there, the plate could  
> be cracked, or the pinblock separated from the back, etc.
>
> If the structure is solid, it might be a good time to do a "blind"  
> pitch raise first. Find out how much the pin needs to move to get  
> the pitch fairly close to target. Then move the rest similarly, but  
> less in the bass. At least that will get you closer, and it will  
> take just a few minutes to do that.
>
> Things are going to change a lot as you add tension. Therefore, set  
> your goal to get closer and closer. I'm an aural tuner, but haven't  
> had a pitch raise that large yet. (The largest so far was about 130  
> cents.)  I'd figure on at least 3 passes and leave it in a musically  
> decent but not finely tuned state. In other words, just get it in  
> the ball park the first session. Then I'd come back in 1-2 weeks and  
> try a fine tuning. But it may well be you'll have to do another  
> small pitch raise the second session.
>
> -- 
> JF

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