Johann (Georg) Andreas Stein, (Heidesheim, 16 May 1728 - Augsburg, 29 February 1792) was an outstanding German maker of keyboard instruments, a central figure in the history of the piano. He was primarily responsible for the design of the so-called "Viennese" fortepiano, for which the piano music of Haydn, Mozart, and the early Beethoven was written.
He learned his trade in part at the Silberman workshop in Strasbourg (1748–9), working for Johann Andreas Silbermann, nephew and pupil of the great instrument maker Gottfried Silbermann. He settled in Augsburg, where he also served as an organist.
He built not just pianos, but other keyboard instruments, some of them of novel invention. One extraordinary instrument, called the "Poli-Toni-Clavichordium" (1796), combined a large harpsichord having four choirs of strings (registration 8', 8', 8', 16') with a piano. He also built (1772) the "Melodika," a small organ in which the player's touch could alter volume; thus it stood to regular organs much as pianos do to the harpsichord. He also built "vis-à-vis" instruments, with a piano and a harpsichord facing one another in a single case.
Toward the end of his life, Stein's business was largely taken over by his daughter Nannette (see below). Pianos with his name after 1790 are held to be Nannette's work, as Stein was himself too ill to build instruments by this date.
The Prellmechanik action
Stein's most important innovation, his piano action, was perfected around 1781. This is the so-called Prellmechanik with escapement. In this arrangement, each hammer was mounted on top of the key, with the head on the end closer to the player, a traditional arrangement in German pianos of Stein's day. The hammers were like small, asymmetrical levers, with the hammer head far from the fulcrum, and a small upward-facing hook ("beak") on the other side of the lever, much closer to the fulcrum. When the player depressed the key, the whole hammer assembly would rise. The beak would engage an escapement hopper attached to the keyframe. The escapement hopper pulled down on the beak as it rose, in turn causing the hammer (the other end of the lever) to fly upward and strike the key. The escapement hopper was hinged and sprung; this permitted the beak to move downward past it as the key sank back to rest position.
Latcham (see Grove reference below) calls this invention "a breakthrough in the piano's history;" it "offer[ed] the player a remarkable control of the hammers, especially when playing softly, and [wa]s astonishingly responsive to the player’s touch."
