My wife plays the piano a lot, but the piano seems to go out of tune over the course of a year or so. The old piano tuner dude who used to come and do it has stopped responding to calls/messages and we haven’t been able to find another locally.
There are a couple of really bum notes at the moment and I just wondered if I might be able to give them a tweak myself.
How big is the potential for completely screwing things up? It’s a 100 year old piano (upright) and there are 2 or 3 strings per hammer.
I have disassembled the piano a few times before when we moved house (France > Scotland > France) including removing the keyboard, so I have an idea of the mechanics of the thing.
I have a digital guitar tuner (may be some use?!) but not much other info to go on.

I suspect dialling in a couple of notes will be easy ish. Getting it to play it’s best and give the best sound much harder. Far more in akin to setting up a very complex guitar

You can treat it like trying to true a wheel, give it a go and if it doesn’t work then call a professional as you’ll get charged the same regardless.

The likelihood is that being old it will be tuned below concert pitch (A=440). There comes a time when old pianos won’t hold the original pitch. So consider that when using your guitar tuner. Check what pitch adjacent notes are, or probably better to tune it by ear.

“I suspect dialling in a couple of notes will be easy ish. Getting it to play it’s best and give the best sound much harder. Far more in akin to setting up a very complex guitar”

That.

It’s quite difficult to tune a whole piano as it’s not quite as easy as having an exact frequency per note.   Once you get away from the notes around the middle then the others can be slightly stretched away from what you might imagine because they are trying to match the harmonics of other strings and there are a couple of different ways that they are generated.

The guy who tunes our piano now uses an app after years of swearing by a tuning fork, but it isn’t a cheap app and he still uses his ear and then records the notes for each piano for the next time he visits

but, for a few notes I would give it a go.  Why not

I have disassembled the piano a few times before when we moved house (France > Scotland > France) including removing the keyboard,

And it keeps going out of tune you say? 😉

The likelihood is that being old it will be tuned below concert pitch (A=440). There comes a time when old pianos won’t hold the original pitch. So consider that when using your guitar tuner. Check what pitch adjacent notes are, or probably better to tune it by ear.

100% this. I bought a tuning kit online for an old piano. Used a guitar tuner and started somewhere in the middle and methodically tuned away to concert pitch. It wasn’t until I got about 5 or 6 notes in feeling pretty pleased with myself that I realised instead of just tuning the duff notes relative to the rest of the piano, I was now trying to retune the whole thing. It was a nightmare.

The guy who tunes our piano now uses an app after years of swearing by a tuning fork, but it isn’t a cheap app and he still uses his ear and then records the notes for each piano for the next time he visits

It’s quite impressive that isn’t it – a measure of all the harmonic content

At £100 a pop for tuning, it soon became apparent that a decent second hand digital piano was a better option, especially as we need it for accompaniment for other instruments.

The likelihood is that being old it will be tuned below concert pitch (A=440)

Yes, I was aware of this, and thinking about it that means the guitar tuner will be useless.

Amazingly after doing Scotland > French alps and reassembling the piano was still in tune!

Unfortunately it’s going out of tune (I think) because it gets some afternoon sun in its current location unless we shut the shutters (which makes the room very dingy). There isn’t really anywhere else in the apartment it could be moved to.

If I knew what % A was below concert pitch could I work out what frequency all the other notes should be tuned to?

Depending on the tuner you can sometimes change the reference pitch from 440 down to 436 or whatever – the TC Electronic polytune does this for example

However there is limits to the maths of frequency alignment for the notes of a piano because the equal temperament system is theoretical that the 12tone system doesn’t perfectly match, so the further you are away from 440 you are, you’ll struggle to get even ratios. I would just try to identify the worst offenders only (there is also more than one string to a note..)

https://en.wikipedia.org/wiki/Piano_tuning

surprisingly good wiki article

Find someone with an in tune piano and tune it to that?

best thing to do is find the worst offender and tune that relative to the octave above and below, but if you think that these above and below notes are also out then you’ll struggle to find enough reference tones, you could use the fifth as alternate references but this gets tricky because the harmonics are not quite the same.

I’d find another tuner, or at least get advice from another pianist

I think I’m right in saying that when you have.more than one string they are tuned slightly differently to each other. Plus mean tuning means the harmonics are slightly out (5ths a bit flat, fourths a bit sharp), clearly not something one can learn quickly.

Look into equal temperament tuning before you go any further!

She might end up playing all the right notes, not necessarily in the right order

I gave it a shot this evening. Where the “dodgy” notes had 3 strings I plucked them one at a time and found two were the same and one was out. Made that one match the other two and the key sounded good again.
There were a couple of keys with two strings (low notes) that were dodgy. I made the string that was flat agree to the other one and they sound ok now.
I also found 4 broken strings, all at the top end, and all on keys where there are 3 strings per key. I’m thinking that replacing those is definitely a job for a pro, but not too worried about them at the moment as they are keys that don’t see that much use and don’t sound too bad anyway.
I’m chalking it up as a win.