About 1720, Christofori finished his real pianoforte. He contstructed a much stronger case than had been used for harpsichords, to withstand the increased strain of the heavier strings. The action in this piaoforte shows important improvement over his model of 1707. He added the escapement device, a back check, regulating the fall of the hammer, and connected an individual damper for each note direct with the hammer action, thus giving the performer a mechanism with which he could, through his touch produce a delicate pianissimo and also a strong fortissimo, impossible on either clavichord or harpsichord.
*(From " Pianos and their Makers" by Alfred Dolge, published by Dover Books).