During the investigation of the history of our very old piano made by Franz Oeser from Vienna, we dove in the mechanics (action) of the piano and found that it is partly responsible for the typical sound. We didn't know this when we decided to create a virtual instrument out of the piano. But apparently this is part of why people are triggered by the unique sound it makes.
The action is a Prellzungenmechanik, more widely known as the Viennese action, as developed by Stein-Streicher in 1780. It has an individual escapement mechanism and a check. This action was appraised by Beethoven and Mozart and many others because of the brighter and distinctive tone (still very warm to our modern taste) their action generated. This was especially preferred by musicians of the classical tradition as well as for chamber music, because they blend exceptionally well with stringed instruments.
Mozart owned a Stein piano from the father of Nannette Streicher - Stein, Johann Andreas Stein. Beethoven's most important of the early Sonatas is the Pathétique, which demanded a wider piano, stronger frame and more resilient strings. Nannette Streicher - Stein made pianos to accommodate Beethoven's needs.
Looking into the history of the piano and its mechanics is super educational. And luckily the digitalization of many old documents help us to search for many interesting details regarding such old developments.
For reference I've added the schematic drawing of the Stein-Streicher mechanik from 1780, which is the same action as our piano.
David Crombie even wrote an article on World Piano News on this subject: https://www.worldpianonews.com/general/explainers/early-piano-actions-and-the-oeser/
Our founding lead to more historical diving and we found a book from 1911 describing the characteristic of the Viennese action. To quote Alfred Dolge, who wrote "Pianos And Their Makers":
'Meantime, Johann Andreas Stein, and his talented daughter, Nannette Stein-Streicher, who was not only an excellent musician, but also a thoroughly practical and scientific piano maker, had improved the Schroter action so materially that the grand pianos made by them from 1780 on, were preferred by Mozart, Beethoven and other masters, perhaps mainly for the reason that this action not only had a more elastic touch than the Christofori English action, but that it produced a more sympathetic tone, reminding of the clavichord tone, which all the great players of that period admired so much. This sympathetic tone could only be produced with the Vienna action, because the hammer, when striking, would to some extent graze or draw along the string, while the more forceful attack of the English "jack" action is a straight and direct percussion. These two elements, the pleasant light elastic touch, and the charming musical quality of tone, assured the Vienna grand pianos (flügel) supremacy in Germany, Austria and Italy for many years.'