Bartolomeo Cristofori, an instrument maker in the service of Ferdinando de' Medici in Florence, invents around 1700 the first keyboard instrument with a hammer mechanism allowing dynamics to be graded according to the force of the touch — the gravicembalo col piano e forte, later abbreviated to pianoforte and piano. The three surviving original instruments date from 1720, 1722, and 1726. The inventor is described in a Medici inventory of 1700. Cristofori's piano replaces the harpsichord's plectrum mechanism with an escapement-hammer mechanism, an innovation that was not so much improved at first as refined during the 18th century by Silbermann and Érard.