Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Piano goes sharp -- how is this possible?

Rebuilt 1981 by Groff Piano. I find that Warren Groff, Sr., worked in Colorado City, so how it got here I don't know. I expect a reputable rebuilder would restring every antique instrument. I must say the original strings on my anonymous square piano don't look any worse.
True, this is the Concert Grand's first summer in Richmond, Indiana, so it may take a while to settle down.

a442 at shop...New environment...etc.
The shift up in pitch is to be expect- as has been explained to you.
One cannot simply lower the pitch and expect the instrument to stay there, after that it has been sharp for so long.
Try simply tuning a piano that is only a few cents off of A-440 after it has not been tuned regularly...It's going to fight you. The steel wire wants to return to where it was. As Peter explained, you have to overshoot your target in lowering the pitch, because of this factor.
Then expect to have to tune it regularly until it settles in at that desired pitch.
What you describe as happening is all perfectly normal and to be expected.

Oh, well. I still don't understand how the harp can PUSH on a string and make the pin screw itself IN. The other way, going flat, yes, it pulls. I have seen a bass string on my square rotating the pin back to where it was comfortable, going "ching -- ching -- ching" all the while.

Crown, down bearing. Climate. Pitch change.

It's like an archery bow. Basic physics requires opposing forces to be in equilibrium: Not only is there ~165lbs of tension on the string but there is also 165 lbs of compression in the piano structural elements. If, for example the string tension is lowered to, say, 160 lbs, there is 5 lbs of excess compression in the piano structure that is no longer balanced by string tension. So, it has to go somewhere -- and the where that it goes is into string tension. So, now you wind up with maybe 162.5 lbs of string tension and 162.5 structural compression so that the opposing forces are now once again in balance. Same thing except opposite for increasing tension raising pitch. (These are strictly imaginary numbers for purpose of illustration)

Secondly, in my experience, large high-quality pianos are more sensitive to pitch changes than small cheap ones. So, whereas it may be possible to change pitch 10 or 25 cents and yank a console into passable stability, a change of 3 beats per second at A-49 in a concert instrument is a major pitch change which will not and cannot be stable in a single pass. I think it's not just that it is not as stable of an instrument but rather that a finer instrument in a more demanding situation shows up the little things that would be passed by in a lesser instrument.

Ed,
Having gone through a long learning period both theoretical and practical of the tuning mechanics I sympathise with your concern. I believe that your technique has a flaw that is resulting in the frequency increase.

You will be aware that each string has a speaking length (SL) and a non speaking length (NSL). Because of friction at the pressure bar or agrafe the SL and NSL tension after tuning is not and must not be equal. This is because the lengths are different and hence on stretching the string whilst tuning will leave the NSL higher in tension than the SL. However if the NSL tension is too great and if the string was left in this state and the note was struck hard , the pressure bar friction might be sufficently low that the "excess" NSL tension would be lowered that is transferred (added) to the SL tension resulting in the note frequency increase.

Now you said that you reverse the tuning direction "down to consonance". I take it you mean down to be in tune? However due to the different SL and NSL tensions you actually have to apply sufficient "lowering" tuning torque such that when the note is struck the excess NSL tension is not transferred to the SL and the note remains in tune.

My guess is that you are raising the NSL tension too high and when lowering it to the final in-tune the pressure bar static friction eventually (not during tuning) gets overcome and some of the NSL tension get transferred to the SL raising the frequency.

Ian

Right, if the strings aren't rendering the piano will go out of tune as you play it. I'm not having that specific problem now. At the higher pitch (A 442) several unisons would go out of tune, with the middle string being slightly flat. That's what I've avoided so far with the lower pitch.
If it wants to stay at A 437, I certainly will let it.