A plan of a new invented patent-piano-forte , with additional keys &c. A new Royal Patent on additional keys &c manufactur’d by Longman & Broderip N.o 26 Cheapside, & N.o 13 Hay Market: London
London: , 1794
Engraved advertisement, half-sheet, image 239 x 370mm; plate mark not visible; leaf 250 x 400. Fleur-de-lys watermark. Blank margin clipped on left, old folds.
The second state of the engraving submitted with William Southwell’s patent application, used as an advertisement for pianos made by Longman and Broderip incorporating his inventions. Southwell’s patent incorporated two innovations: captive, wire operated dampers, and an extended range. This type of damper superseded all previous designs and is the ancestor of the modern grand dampers. The range of the standard square piano was extended by more than half an octave in the treble with 8 extra keys (f3–c4) without increasing the length of the instrument. These innovations were patented in 1794 when Southwell moved from Dublin to London and immediately taken up by Longman and Broderip. The patent application copper plate was reworked, replacing Southwell’s name with Longman & Broderip and the lion and crown of England in place of the Irish harp in the triangular area behind the wrestplank (Michael Cole, The Pianoforte in the Classical Era, 1998, pp. 104–5). A later state of this engraving, used by the firm of Broderip and Wilkinson after 1798, is illustrated by Richard Burnett in The company of pianos (2004) on p. 70.