French horn, lip vibrating air sounding instrument. Also known as French horn. Brass instruments widely used in symphony orchestras and military bands. Copper spiral tube body, funnel-shaped nozzle and large bell mouth. The classical horn has a pitch of F or B flat, and has three valve keys (vertical and rotary). The natural overtone pitch of the horn is reduced by increasing the length of the pipe. The valve key enables the player to play all semitones from bass B to treble F. The horn is a transposed instrument, and the notation is made by a treble spectrum, which is five degrees higher than the actual sound. The most commonly used horn in modern times is the F-key, and many musicians use the double-key horn. This horn has a valve key controlled by the thumb of the left hand to increase the length and turn the horn from the F-key to the B-key in the lower bass range. The horn player can insert his hand into the horn mouth, which can not only reduce the volume but also change the timbre to form a blocking sound, or use a pear-shaped mute without changing the pitch. After using blocking sound and mute, the volume is reduced, and the timbre is gentle and dim when playing weakly, which has a long-distance effect, and it gives off a rough and cracked sound quality when playing strongly. The modern French horn was developed from the French hunter's horn around 165. In order to play various tunes on a horn, the player once installed a pluggable tube under the horn mouth, and German A.J. Hampel improved this device. In the 17th century, he entered the orchestra. In the early 19th century, the direct valve key was invented by F. Blummer and H. Stelzel, and was adopted by many producers. In about 19, the newly invented double-tone horn replaced the favorite F-tone valve key horn. The sound of the horn is soft and full, and it can be well integrated with the sound of woodwinds and stringed instruments. In a symphony orchestra, four horns are usually used.