Hi Calin. In many original Pleyel pianos in the 1840-1860 range, I noticed that, when tuned at 440 Hz, in the 5th or 6th octave, some notes have a funny, tubby sound, just like if the strings were not tensionned enough. On the one I have, when tuned higher, this disappears, and the sound comes back to something more normal. Unfortunately, on a piano with original (or very old) strings, I hesitate much to do breaking tests, unless I have to restring anyway. For Bechstein, I am quite sure that from the beginning they used Krupp steel similar to modern steel, and kind of low tensionned : on a 1871 Bechstein with most probably original strings, the strings average broke at a minor sixth above the note's right pitch referred to A4 = 440 Hz, which the new Röslau strings did too. That was the motivation of Carl Bechstein : build a piano that could hold up under the agressive powerful playing of Franz Liszt, who liked breaking strings in front of young ladies. On the Pleyel 1864 I'm restoring now, I'm not sure that the strings are original. But they broke average an augmented fourth above the 440 pitch, while Röslau for the same note, same diameter, broke a perfect fifth above, and the Pure Sound broke as soon as somewhere between a major third and a perfect fourth above. Maybe these strings were end 19th Firminy wire, as I know the piano has been upgraded at the Pleyel factory about that time. Anyway, in your situation like in others, I would trust my ears, and try to reach the best sound, which I'm sure they did too at the factory. Not enough tension = funny sound, more tension = cleaner sound (less inharmonicity due to increased elasticity of wire), too much tension = much less sustain, sound getting thinner (less personality) and strings breaking on heavy playing. (Ah, and also structural integrity of the wooden parts sooner prone to failure.) Best regards. Stéphane Collin.
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