 The second instrument was built by Flight and Robson in London, and used moveable shaders close to the mouth of the pipes in order to lower their pitch temporarily by one or two commas which reduced its cost and size, and with an improved bellows the system it was the subject of a patent granted to Liston and Charles Broughton on 3 July 1810.After introducing the instrument in a session at the builder's showrooms in 1811, Liston published his "Essay on Perfect Intonation" (Edinburgh, 1812) describing its tuning, construction and operation along with a treatise on music theory and 40 pages of music .Liston also patented an improved plow on 23 September 1813, claiming a special shape and an inclined wheel, which was locally used.