I tuned a clients Kawai CX-4S console today. I tuned it for the first time last year and today it was right on pitch. I was impressed. There was a considerable buzz at Eb3. When played softly, it wasn't noticeable but under a moderate or hard blow, it was very noticeable. I pulled the piano away from the wall and checked for loose objects. I tightened all hinge screws and soundboard buttons and checked hinge pins. Inside, I tightened and checked the trap work. I pushed on the strings and bridge pins and pressed on the soundboard all over while sounding the note all to no avail. I checked around the area for sympathetic vibes but came up empty. I checked over the action and all seemed fine there. I tried plucking the strings while the action was out and couldn't hear the buzz. I had another appointment and had to leave it. Any suggestions?
Much appreciated
John Pengelly
The Tuning Fork

John,

I think this is a model with two action brackets, right? If so, at the treble break, there may be a screw that goes through the aluminum action rail to the plate as support. It should have a rubber cap where it contacts the plate. These screws have come loose on a couple of Kawais I've seen, causing a rattle. If that's the case, just tighten it enough so that it touches the plate without pushing hard. The reverse force on the screw can bend the rail outward.

Worth a look.

That's a new one on me Dave. Have to keep a "ear" out for it. Thanks. For a Kawai I would bet on hinges for a buzz. John, are you sure it is not sympathetic? Somewhere in the room, on the wall, etc.?

I've actually seen it in two pianos. The noise was driving everyone nuts, but we couldn't find anything. Finally, while tuning the piano, I heard the sound come from a very specific place at that screw. Sure enough, the screw was loose and had backed out of it's hole. The little plastic boot that goes against the plate had fallen onto the keybed, too. Don't tighten the screw too much, though, or you'll tweak the action rail and mess up the regulation big time. I put a couple of dabs of water soluble glue on the threads so it wouldn't back out again.

Worth a look, anyway.

I did check the hinges and for sympathetic vibes. I will check out your tip Dave the next time that I am in the area.
Cheers
John