Old Bechstein keeps slipping out of tune

Musikell

The pianoscope app is a great help and I was thrilled with early results, feeling it was a vast improvement on the state of the tuning after the last visit from a professional tuner.

However I am finding my 1922 Bechstein model A does not hold its tune very well, especially after extended playing with other musicians. In the (very lively reverb) room it sounds fine but when I record it the results are dreadful - unless I am being unfair by comparing it to my Nord Stage 2.
I record with 2 Aston starlights and a Neumann U87ai.

The strings also click when tuning so that I go from flat to sharp and back to flat again. After a long fight I finally get a decent sound, but a few days later some notes go out by up to 5%.

Has anyone any ideas? Might it settle down if I keep tuning every few days?

Frank Illenberger

If the notes go sharp soon after tuning, it is most probably because you left the tension in the non-speaking part of the string too high. This is to be expected if you have just barely learned how to get a piano in tune and have not yet learned how to pay attention for the so called "setting of the string". If I can find some time, I want to write a tutorial on this topic, but this will be while.
The main effect happening when you approach your tuning target from above - going sharp first and then easing down - is, that once you release the tension on the tuning hammer, the pin untwists a bit and the hammer unbends a bit. This results in a rise of the tension in the non-speaking length of the string. The friction at the agraffe or pressure bar then prevents this higher tension from slipping through to the speaking part. But once you start playing the instrument, this friction can be overcome and the tuning goes sharp. You have the opposite effect when approaching the tuning target from below. How strong this effect is depends on the length of the non-speaking length which varies strongly between different instruments and strings. It also depends on the friction at the agraffe and the friction of the pin in the pin block.
There are several techniques to counteract this effect. The easiest (but inelegant) way is to play hard blows once you have reached the tuning target to "test" whether the tuning is already stable. With this approach you might have to retarget the notes a couple of times, but you will obtain a stable tuning.
Other more efficient techniques apply an additional bending to the tuning pin which cancels out the untwisting effects. Professional piano technicians have lots of experience in getting this right on different instruments and a lot of muscle memory for it.
From my conversations with tuners I found that some are are having more or less esoteric views on this issue. Some claim that the pin itself has to be "set", but I doubt that this is backed by physics. But as I am not a professional tuner myself, I am not an expert on this. Professionals in this forum will most certainly have much more experience than me and a dedicated opinion on this.

Until I find time to write a tutorial, the only online resource on this I know is a paid video course by Mark Cerisano which is explaining these effects in depth. https://howtotunepianos.com/superior-stability/

Musikell

Thanks for this Frank. I had a look at the link - How Much??
I’ll keep on tweaking,

Frank Illenberger

Musikell Yes, I know 😀 I think this video course is targeted at professionals who want to hone their technique. Simply start by rigorously applying test blows. This will get you quite far.

Paul

Musikell Marc Cerisano has a lot of videos available on YouTube - but they are slow and a bit confusing and he makes many mistakes with his own tuning systems. There's some good information in them, though.

Stefan Borowicz

@Musikell If you do a search for Mark Cerisano on YouTube, you will find any number of videos he has done that address his method to some extent—at least enough to get the idea...without paying for his course.