 In November 1794 Érard filed the first English patent for a harp "(Improvements in Pianofortes and Harps, patent no.2016)", a greatly refined single-action instrument (tuned in E flat) that could be played in eight major and five minor keys thanks to its ingenious fork mechanism which allowed the strings to be shortened by a semitone.Érard's "double movement" seven-pedal action for the harp (perfected and patented in the summer of 1810, "Patent no 3332") allows each string to be shortened by one or two semitones, creating a whole tone.