The original horn was simply an animal horn. The word for "horn" in German is "horn," in French "cor," and in Italian "corno." The terms "cor" and "corno" originally meant an animal's horn, directly expressing the animal origins of the horn. It is most likely that people from ancient times turned the horns of their prey into musical instruments. This description both explains the origin of the horn and the etymology of the word "horn." There are many other musical instruments that bear the name "horn," but today, the instrument known as the horn is commonly called the "French horn".

Until the middle of the sixteenth century, the horn was used by hunters as a means of communication during the hunt, and thus the body of the horn was wound in large coils so that it could be carried on the shoulder and sounded while riding a horse. In addition, the bell faced to the rear to keep it from getting in the rider's way.
The horn is very similar to the trumpet in that sound is produced through the vibration of the lips. Maybe that is why the horn has a history of development almost identical to that of the trumpet.
Horns made up to the middle of the nineteenth century are called "natural horns" because of their simplistic structure, which consists of a large bell, a single coiled tube, and a mouthpiece.
The pitch of this type of instrument can only be changed by changing the vibration of the lips, and even then it is only possible to produce a tone referred to as a "natural harmonic." This of course means that it cannot play musical scales. This state of affairs drove the players of the horn to think of sticking a hand in the bell to produce a tone other than this natural harmonic. This way of playing the horn, called the "hand-stopping technique" developed among horn players in the eighteenth century.
Despite the new hand-stopping technique, the range of tones possible with the horn was still very limited, the tones and pitches were unstable, and the timbre had a muffled quality. The resolution of this problem came in the mid-nineteenth century with the development of what was known then as the "valve horn," a horn whose effective length could be altered instantly by opening one or more valves like those on today's modern instruments.
With the arrival the valve horn, horn players could now easily play a stable chromatic scale.
The end of the nineteenth century saw the invention of the double horn, which combined two tubes of different lengths, and in the twentieth century, the triple horn was invented.

The horn family

The F single horn

This is the F single horn, or F horn. The basic pitch of the F horn has a unique, beautiful timbre.

The B♭ single horn

This is the B♭ single horn, or B♭horn. The pitch of the B♭horn is four steps higher than the F horn, and so this horn has a brighter, clarion tone. Horn music is written in the key of F, and so transposition is necessary when playing the B♭horn.

The F/B♭full-double horn

The F/B♭full-double horn, the most common and widely used horn today, can produce both F and B♭notes from a single instrument, and can produce both F and B♭ timbre.

F/B♭ semi-double horn

The F/B♭semi-double horn consists of a B♭tube and a supplementary F tube, and as a result it is lighter than the full-double horn.

The B♭- High F descant double horn

The B♭- High F descant double horn has the same structure as a full-double horn, but instead of a standard F tube, it has a half-length high-F tube that allows this instrument to perform in a higher tonal range.

The triple horn

The triple horn is really a full-double horn with a high-F tube for playing in the higher ranges, and though the overall tonal range is unchanged, it is more stable in the higher range. The B♭tube is the primary tube, with the player switching to the other tubes as necessary.