Prellmechanik and German Action (Viennese)
In both the above types of piano action the hammers pivoted in a kapsel fixed directly into the rear of the key. The head of the hammer faced the player, whilst the butt, which was shaped rather like the beak of a bird, was towards the back of the action.
When a key was pressed, the hammer would rise and its tail would be forced into contact with the Prelleiste rail, that was fitted to the rear of the action. The hammer tail was forced downwards by this rail and consequently the head would rise and strike the strings, rather like the motion of a se-saw.
The Prellmechanik had a continuous rail for engaging the hammer butt, whereas in the German or Viennese action this rail was divided and individually sprung, one for each note.
The Viennese action was really a more sophisticated and advanced type of Prellmechanik. It was with a piano using this type of action that the great musician and composer W A Mozart would have been familiar and composed his piano music. The Viennese piano was light in construction and usually bi-chord throughout, with light leather covered hammerheads. The instrument would have had a light delicate tone.
The invention of the Prellmechanik action was attributed to Silbermann, whereas the invention of the German or Viennese action was the work of Andreas Stein in 1773. Stein was a pupil and apprentice to Silber