LvB died in 1827...

Sorry about that - the reference work (The Library of Piano Classics - Copyright 1987 by AMSCO Publications) I used to check this said 1817 - but that would appear to be a typo according to other sources.

sigasa wrote:

https://youtu.be/jnL9PIMH1nk

it's thought that felt was only first used around 1825 - a good 8 years after Beethoven died
...
Also, as a side, Sébastien Erard didn't develop the 'double escapement' action until 1821

LvB died in 1827...
smh

Interesting, but they used precision electric tools for precise cut and sand the wood.

Interesting indeed. I'm sure Erard used the same tools as well when the piano was first built. :-)

https://youtu.be/jnL9PIMH1nk

Fascinating - I wanted to hear it fully at the end [sniff]

The small sample I did hear had a very bright (loads of overtones) and quick decay to the upper notes especially - they seem to get lost quite easily against the more powerful bass notes.

Now, I couldn't tell from the video what material was being glued to the hammer heads, but it's thought that felt was only first used around 1825 - a good 8 years after Beethoven died - before that leather was the material of choice !

Also, as a side, Sébastien Erard didn't develop the 'double escapement' action until 1821, but the 'back-check' was around to stop hammers double/triple bouncing against the strings during loud passages.

Thanks for sharing !