The piano I'm having a problem with is a 30 yr old Kawai KG-6C or something like it. The problem is similar to Al's thread with only the capo sections going out, the agraffe sections are rock solid. Three years ago I re-strung both capo sections because of false beats and hoping to help the tuning stability. At that time I redressed the capos. The piano was much better, with frequent tuning for a while but now has slipped back to it's old problem. The piano is in a church and gets heavy use but I think the treble sections would need to be tuned twice a week to be stable. I may try that. Fenton ----- Original Message ----- From: "Ron Nossaman" <rnossaman at cox.net> To: "Pianotech List" <pianotech at ptg.org> Sent: Saturday, July 12, 2008 11:07 AM Subject: Re: Tuning a Kawai Grand RX-2 > >> I'm interested in this thread because I've a similar problem with a >> Kawai. >> Ron, >> Backscale, sounds reasonable then to stretch and settle the back >> scale.?.? >> Fenton > > I don't think so, because the back scale isn't unstretched or unsettled. > The line of thought that, in thirty years, has gotten me to this point is > this: When the slightest movement of tuning pin by the hammer results in a > detectable change in speaking length pitch, and you can easily control the > thing, by speaking length pitch and the feel of what's happening in the > hammer, and it survives whatever test blow(s) you're fondest of, your > problem isn't from the speaking length bridge pin forward. Why? Because > you've moved all that, felt it move, heard the results, and being a > competent tech with some years' experience, left it in a stable state. > What you don't know, and what no amount of magic hammer technique will > EVER tell you is the condition of the segments behind the front bridge pin > row. You have no way of ascertaining what's waiting for you back there - > NONE. You can't feel what's there because you likely haven't made a big > enough tension difference during tuning (unless you raised pitch > substantially), to overcome the bridge pin friction points and detect the > resulting movement. So you basically take what you can get. If you pound > too hard during tuning, you can pull some of that back scale through the > bridge, leaving the rear segment tensions higher than what you settle the > front lengths to by listening to the speaking length. Later, with the tiny > movements of temperature and later humidity changes, the tensions will > tend to equalize some and the speaking length will go sharp. If the back > lengths are of lower tension when you tune it (which you can't know) and > you can't manage to pull the string through the bridge with test blows, > the speaking length pitch will drop later either by those same temperature > changes, or by someone hitting it harder in play than you did tuning it. > Where do you suppose the pitch drop comes from when a test blow knocks the > tuning out? Being a competent tuner, you left the front segments in good > shape, so what happened. The back scale happened. The back lengths are a > real crap shoot. Sure, you can push on them massage them, stretch them, > yell at them, or anything else you want to try to drive out the evil > spirits, but the bottom line is that when you have no way to directly > compare the front and back length tensions, you have no way of know if > you're improving the situation or making it worse. The only way I know of > to produce a dependably stable tuning is to tune often, on a piano that is > under rigidly controlled temperature and humidity conditions, and move > things as little as possible doing it. > > I'm, on the way out the door, so won't take the time to proof this for > psychotic sentence structure or strange inside out disconnections. If > there are any, sorry. > > That's essentially it. > Ron N > >
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