Hello, I've been a member of this forum for quite a while, but I haven't posted anything in a long time. I finally bought an inexpensive acoustic piano two weeks ago, that's about 40-50 years old. A piano tuner helped me choose it. Basically it's a piano built in the Soviet Union, so I know you don't like those already, but anyways ...
The same tuner came to my home to tune it last Sunday. I was warned that some string might break because it had been kinda neglected before, so of course 1 of 2 string broke on an E2 key, and one out of three on a D#7 (that was unexpected, because he said bass string are more likely to break), either way that's not the problem. The piano sounds nice and is holding the tune as of now, except for the F# of the second octave, it went flat 15 mins after the tuner left. So I opened the cover and I muted seperately each out of two strings with an eraser and individually they sound in tune, but when hit together they're not. So for now, until I will get the tuner to come in and most likely change the tuning pin(s) for that key, I was thinking I could mute one of the strings, but I don't know how I can do it without muting any other surrounding strings?

You can't. You will have to lose one of the neighbouring strings as well.

If you are bright and have the interest, why don't you get a tuning hammer and try to tune the unison yourself. Here are some caveats:

Do not move the pin more than 5 degrees. That will hopefully prevent you from breaking a string. Which brings me to...

You may break a string.

If you can hear it sounds out of tune, there's no reason why you couldn't improve upon it, if you don't mind dealing with the trouble you may find.

If you can't get it to sound good (remember, no more than 5 degrees) then just mute it off.

Warning, there are going to be some technicians who reply to this post and say this is the stupidest thing any technician ever advized anyone to do.

changed my mind.

Formidable!

I don't think it's stupid at all. Curiosity is how many of us began learning how to tune in the first place (or for that matter, learned how to do anything).



Evaldas, any one string will always sound in tune, because there is no reference point. If you do take Mark's advice and try to tune one of the strings, make sure you know which string has actually gone flat. Play the F# above it and see which individual string sounds best with it. Maybe neither - maybe they both need to be adjusted.

This is all very crude advice, of course. There is much more to accurately tuning a piano - but if you can get your hands on a tuning hammer and have the inclination to experiment, you may be able to at least improve it while you wait.