Let's face it, we know less than we think about what 19th century pianos really sounded like
Slate currently has an article posted that compares the sound of the modern piano with that of its progenitors that inspired Beethoven and Chopin, among other great keyboard composers. Included are sound samples to help us hear the differences.
My favourite examples are of late Brahms (the Op. 119 Rhapsody) and Debussy (Feux d'artifice).
The article questions why we seem to want a "standardized" piano sound these days. But it fails to address the vast differences that one still hears in pianos. Despite the company's continual protestations to the contrary, a new Steinway concert grand from New York does not sound or feel anything like one made in Hamburg (not to mention all the variations from piano to piano). And there are marked differences in sound between a big, brash Baldwin grand and a burnished Bösendorfer.
Another question I have is why the people who work with historical instruments almost never mention the fact that the felts and strings that inevitably have to be replaced today to keep those pianos playable are of a different composition than materials of the 19th century.
When he needed to replace the bass strings on my piano, my dear, retired piano technician, Bill Goodfellow, spent a lot of time explaining to me how the metal used in strings today is superior to the original, providing a fuller sound. The old strings were tired, too, after a century of being stretched to within a hair of their breaking point.
We think we know what Brahms's piano sounded like, yet we really have no idea. But the guessing game can be fun.