CAUT

  • 1.  Three tuning conundrums

    Registered Piano Technician
    Posted 02-16-2022 11:51
    Greetings all,
    1. When tuning grands, I often successfully eliminate false beating by massaging the string just in front of the bridge. However, I'm wondering why the pitch falls, often by 10-15 c.

    Intuitively, would seem to be two possible reasons. The first is that if the string were slightly higher on the bridge, pushing it down would release tension. The other possibility is that putting pressure on the string would pull a bit of string over the tuning-pin-side bearing points whether agraffe or V-bar, making for a de-equalized segment. However, pounding the key should in theory then cause the segments to equalize and the pitch to rise in the speaking length, right? But that doesn't happen. It stays low. It just seems odd that massaging a string should cause that much of a fall in pitch.

    2. When tuning verticals, I generally try to tune middle strings first in the high treble. During pitch raises, it seems to yield stable results. However, sometimes I can't get a mute into the middle string due to hammer/damper clearance or a key cover that's in the way, and I have to tune left-middle-right. In that case, when I go back for the second pass, the right strings are invariably high, often 15 cents. Why is that?

    3. Pitch raises with a Verituner generally come out close to pitch with my usual overpull of 12/28/36. However, when a piano is really low, like 100-200 cents or more, a second (or even third) pitch raise is required. For example, if a piano is that low, I know that when I come back to the high treble it will have fallen again (even with a 40% overpull), often by 20+ cents, thus requiring another pitch raise. But If I use the same percentages on the second raise, often something odd happens: the pitch ends up way too high. Why should that be? Is it the way Verituner calculates the raise? I've started experimenting on the second pitch raise by starting a new tuning file, as if it's the first tuning, and this may help. The jury is still out.
    Anyone else have the same phenomenon?

    thanks!

    ------------------------------
    Scott Cole, RPT
    rvpianotuner.com
    Talent, OR
    (541-601-9033
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  • 2.  RE: Three tuning conundrums

    Registered Piano Technician
    Posted 02-16-2022 12:35
    Scott,
    Concerning your number one, there is a likelihood that you are pulling string through the bridge pins from the hitch pin side. There is a lot of friction between the wire and the bridge pins and surface. It is likely that it is rare for that segment of the string to be in equilibrium with the speaking length, and that strings don't rend through the bridge pins during the process of tuning in the normal parameters of pitch change sufficiently to cause the segments to be equal in tension.

    #2 I see no reason for the difference in left/middle/right in the scenario you present. You might substitute tuning right-middle-left just as an experiment to see whether the result changes.

    #3 I prefer to tune pitch raises so that when I have completed a unison, all strings are at the target pitch. This gives me a more stable result, as I am able to use the ETD to confirm the stability of each string.

    With larger pitch changes, I pull the left string slightly sharp (1-2¢), tune the middle string quickly to the left (aurally), then tune the right string to pitch precisely and with good stability. Now I pull the unison into focus and make sure all three strings are stable. 

    For pitch raises within about 25 cents, I don't find the need to do a second pass, or it is only about 5 - 10 minutes of refining unisons. 

    (Al Sanderson thought that the major factor in large pitch changes, leading to the need of offsets, is the plate being pulled. This is what led him to recommend tuning by half steps left to right, which has certainly shown itself to work very well. We see the principles involved in the broken string phenomenon, where the notes on either side of the broken one go significantly sharp, but go back to pitch when you have replaced the string and brought it to pitch. This is what I keep in mind while I am tuning each unison). 

    This method doesn't work using the offsets given by various ETDs, as those offsets would leave the piano significantly sharp. I set the offset myself, far more modestly: maybe 5% for bass (if any offset), 15-20% for plain wire. 

    With respect to your two pass for more than 100¢ cents, I have seen similar results, and found that often it is best to simply do the second pass straight to pitch, or just a very small offset. 


    Regards,
    Fred Sturm
    "When I smell a flower, I don't think about how it was cultivated. I like to listen to music the same way." Mompou