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After having my Kimball Viennese voiced, I still have one bass note (1st F#) that I would describe as sour, but only as it is struck by the hammer. It cleans up immediately and has clean overtones and sound after the strike. I asked the tuner about it when he was finishing up his regulation/voicing and he muttered something about how some (I think he was trying not to say the word ‘cheaper’) pianos can have a bad note or two. I would maybe agree other than the sound becomes pure after the strike. To me, it sounds like that hammer is shaped incorrectly or is hitting, or releasing from, the string incorrectly. Otherwise, the tune and unisons are all perfect, and the regulation now seems as good as any Schwander could be. Any suggestions? Is that just the way it’s going to be from here on out? I’d rather not put new hammers in it. The strings all look perfect, there is no corrosion or rust anywhere. It literally looks like it left the showroom when I bought it off the little old lady.
But it is amazing how ONE note can ruin everything! Please help

Does that note have one string or two? Badly matched bass strings happen, and the copper-wound bass strings can go dead. Have seen that happen with pianos as young as 10 years and as old as 80. And it happens usually unevenly across the bass notes, when it does happen.

I would agree that most all acoustic pianos have that one note, or more, that just doesn't sound as good as the rest of them.

That said, I'm thinking a really good tech, with a lot of experience, can at least critique/massage or otherwise do something to make it somewhat better, even if just a slight improvement. Maybe at the time the tech was tired/fatigued and ready to move on the next service call.

Based on your description, it sounds like the problem is with the initial impact between hammer and string, and then starts to blend in nicely with itself or other intervals. Maybe a little hammer voicing? Filing, needling, or a few strokes with a brass brush?

I'm thinking that particular note is a single bass string. If nothing else works, maybe loosen the pin, remove the string from the rear hitch and give it a twist or two in the direction of the copper coils? Might be worth a try.

Good luck!

Rick

+1 Some one needs to go through all the possibilities to find the source of the problem. Could you post a recording from your phone of the note played from pp to ff?

This is 99.99% likely NOT the problem, but sounds vaguely like a puzzler in the low bass I ran across once, a voicing needle that had broken off in the hammer felt. I discovered it when *I* stuck a needle in and hit the broken needle.

Just a remote remote possibility.

That happens. You can check with a magnet, if you do not see anything.

It is the lowest 2-string note. The the
single-stringed F just below it is pure. The G above is much much better but not as pure as the F. He double-checked the unison when I brought it up and it is dead on. He did another quick test then also: muted one string, pressed the key but with no strike, then he hit a random fifth(?) midway up the keyboard and released. Both F# strings sounded the same individually. I’m sure I’m not explaining that well.
The more I sit here and play that note, it almost sounds like the strings are out of sync at first and then they match their sine waves a moment later. I’m not convinced it’s the strike anymore

If the two strings are not perfectly matched in terms of inharmonicity, even if the fundamental is perfectly in tune, the upper partials will not be in tune, and will beat loudly enough for you to hear. After a very short time, the strength of the upper partials may weaken enough to make the two strings sound more in tune.

I had this problem on my M&H BB original strings (2009). I couldn't actually tune several of the duples. I replaced the bass strings last year with very fine matched strings and the problem disappeared.

To test, press the key down so both strings can speak and then strike and release any octave, fifth, or third, (or any other note in the high end) and listen for the partials. They will likely be beating.

Download TuneLab trial version and examine the pitch of each string, muting off one of the strings with rubber or felt so you are measuring only one at a time. See if one of the string's pitch vary widely as the note is played. That may get you closer to diagnosing the problem.

Tunelab Download

Would Rick's suggestion of twisting the string change the inharmonicity? If so which string to adjust?

Well, if other things have been tried, to no avail, doing the string twist on both bi-chord strings might be worth a try.

On my Yamaha C7, the next to the lowest C, or the first C bi-chord note has a bit of an odd sound, a little fuzzier than all the other bi-chord notes. The fuzziness/impurity can be improved with some very fine tuning, but it still doesn't sound as good as its bi-chord neighbors. But it does blend in when play music and not focusing on that one note.

Rick

Thank you for the tip, Rick. Yes the partials beat like a throbbing sound when I do that test with both strings speaking. I have a tuning app so I checked the unison and found it off a bit so I matched them and it made a significant improvement. But, that note still has a unique sound, albeit less sour than before. On my app, I noticed the pitch on one string definitely moves around a lot more than the other and the same string has the sour sound at first. Is this just a bad string?

I'm no expert but you might have a loose bridge pin or the string needs to be firmly reseated on the bridge pin. You can test this by firmly tucking the string against the pin with a brass rod (something that won't mar the string) and have someone play the note. This applies to the sour string.