 In this sense, "French horn" refers to a narrow-bore instrument () with three Périnet (piston) valves.It retains the narrow bell-throat and mouthpipe crooks of the orchestral hand horn of the late 18th century, and most often has an "ascending" third valve.This is a whole-tone valve arranged so that with the valve in the "up" position the valve loop is engaged, but when the valve is pressed the loop is cut out, raising the pitch by a whole tone.