Chromatic trumpet and French horn

Chromatic trumpet and French horn the prototype of *duplex instrs.: a double trumpet or French horn patented by Charles Claggett of London on Aug. 15, 1788, consisting of 2 trumpets (or French horns), one in E♭, the other in D, played with a common mouthpiece that could be switched from the tube of one to that of the other instantly by means of a pin projecting from a little box below the mouthpiece (89 Morley-Pegge). Grove's Dictionary of Music and Musicians, 5th edition. London, 1954.