The horns of the Middle Ages took many different forms, from the small horn carried on a strap over the shoulder to the military horn as tall as a man. 

The most commonly used horns in the Middle Ages were:
The medium-sized cow-horn: because of its tremendous volume the cow-horn, which was actually made from a buffalo horn, was used for hunting.
The military horn: curved and made of metal this horn was nearly as high as a man. It had a louder and more booming note than any other horn and was therefore used for military purposes. Its successor is the Alpine horn.
The bugle: this was the smallest of all horns and was made either of animal horn or metal and was used by guards, sentries and shepherds. In courtly circles the more elegant version made of gold or ivory was used.

Instead of a mouthpiece, these instruments had an opening to blow into. Originally only a single note could be produced on the small horns and the first three naturals on the bigger ones. From about 1000 AD finger-holes, which first appeared in England, gradually increased the range of notes, following the example of pipes.

The first coiled horns, the direct forerunners of modern valve horns, were made in Europe, probably around the 12th century. Although coiled horns had already existed in early civilizations the knowledge of how to make them had been lost in Europe during the migration of peoples around 800 AD.

Straight Zink in C, Günther Körber (=signature), wood (Musikinstrumentenmuseum Schloss Kremsegg, Austria, collection Streitwieser)

Baroque horns had cup-shaped mouthpieces which were either a flared extension of the tube mouth itself or a separate fitment to be attached. By half covering the finger-holes a chromatic scale could be played, and the technique of overblowing was also already in use. The art of “cornett playing” was already widespread. The cornett (German: Zink, Italian: cornetto, French: cornet à bouquin)  had evolved from the medieval horns. The cornett had been improved considerably during the Renaissance and the baroque instrument had a thick, usually hexagonal curved tube made of wood and occasionally metal. It had seven finger-holes, which had keys on the larger instruments, and was blown through a cup-shaped mouthpiece. As the soprano of the trombone group the cornett was adopted by art music, especially in the works of J. S. Bach. The cornett cannot properly be called a brass wind instrument as we use the term today because its timbre was considerably thinner and did not possess the metallic character peculiar to modern brass instruments.

The large, single-coil hunting horn that was used in the 17th century (Italian: corno da caccia, French: cor de chasse) underwent its first technical development in France and for this reason became known as the French horn in England. This name was later used for a model of the modern valve horn.

In the middle of the 17th century, when the trumpet was already being used in art music, the horn was still seeing service as a signaling instrument for hunts and battles. One of the reasons for this was that coiled, circular tubes were very difficult to make. To all intents and purposes the hunting horn was a trumpet in the shape of a horn. The tubing was long and narrow and only very slightly conical. The instrument had the same series of natural harmonics as the trumpet of that time. The difference was that the horn’s tone did not possess the metallic shrillness of the trumpet.

The popularity of the hunting horn, the timbre of which was basically no different from that of the trumpet, was mainly due to its coiled tube, which made it a deep instrument that was easy to hold and well-suited for playing trumpet parts in the lower register – at that time the deepest trumpet (in low F) had a tube that was 3.86 m long – hardly practical!

Hunting horn in Eb with 3½ coils, Gaillard & Loiselet, Paris, after 1935 (Musikinstrumentenmuseum Schloss Kremsegg, Austria, collection Streitwieser)

In around 1680 the first hunting horn consisting of several coils and a conical tube made in one piece was constructed in Paris. Jean Baptiste Lully (1632–1687), who introduced important innovations in orchestral techniques (he expanded the string orchestra to five parts and was responsible for significant developments in the minuet and concerto grosso which he helped to international recognition, beside founding the French national opera), championed this improved horn and encouraged its widespread use. His efforts led to the adoption of the hunting horn by orchestras.

From the beginning of the 18th century the hunting horn was used, particularly by Bach and Handel, to play in a variety of registers, including the highest register up to the 16th natural, as was the trumpet. In the orchestra the horn was usually played by trumpeters, parallel to the other commonly used horn of the time, the cornett. By the middle of the 18th century the latter instrument had fallen out of favor, however, and was no longer used.

In around 1700 the hunting horn underwent a fundamental change, principally at the hands of the Leichamschneider brothers in Vienna. This new design imbued the instrument with a new quality of tone, and turned it into the true French horn. Michael and Johannes Leichamschneider widened the bore, thus darkening the timbre which up until then had resembled that of the trumpet, and creating a new, characteristic horn sound. The tubing was made more conical and was coiled four times, making the instrument easier to handle. In addition the new French horn was given tuning crooks, additional sections of tubing between the mouthpiece and tube which tuned it to a different pitch.

Hand horn, William Shaw, Red Lyon St Holborn, London, between 1783 and 1802 (Musikinstrumentenmuseum Schloss Kremsegg, Austria, collection Streitwieser)

Further developments to the French horn carried out by the Bohemian hornist Joseph Hampel (1710–1771) from 1753 gave the instrument the structure and sound characteristics it possesses today. Hampel’s greatest innovation was the introduction of hand stopping for chromaticization.

Anton J. Hampel discovered that the notes of the natural harmonic series could be lowered by placing the hand in the bell, so that the gaps in the natural harmonic series could be filled. This technique gave the horn a certain chromaticism, although it goes without saying that the quality of these intermediate notes cannot be compared to the modern valve horn. For this technique, the bell was held facing downward, instead of on its side or facing upward as in the past, and the right hand was placed inside it. This produced a vast improvement in the sound quality, since stopping eliminated the shrillness and roughness of the horn’s timbre.

The timbre was further refined by the replacement of the cup-shaped mouthpiece by a funnel-shaped one, which gave the horn the mellow and romantic euphony that characterizes the modern valve horn and contrasts so sharply with the strident metallic quality of the trumpet. In 1753/54 Hampel was also responsible for the construction of the first hand horn with slide crooks: on this horn the tuning slides were placed in the middle of the tube, which meant that different crooks could be inserted more quickly, a great advantage for orchestral playing.

In terms of sound, the new French horn was an entirely new orchestral instrument and even took over many of the roles which had previously been the province of the trumpet. Hampel’s hand stopping technique filled the gaps between the notes of the harmonic series and gave the French horn a certain chromaticism; however, the stopped notes were still far from perfect: in places they sounded very dull and could only be used as transitional notes and not for carrying a melody. To circumvent this problem, classical composers either called for several different tunings in one work (in his opera Don Giovanni from 1787, Mozart calls for no less than 36 changes in horn pitch), or they avoided stopped notes altogether. In the late classical orchestral repertoire there are very few notes that would have had to be played using stopping – one exception is the horn solo in Beethoven’s 9th symphony.

Czar horn, Joseph Schediva, Odessa, around 1884. This gold-plated horn with engravings (flower ornaments, Russian two-headed eagle and St. George) was built specially for Czar Alexander III (Musikinstrumentenmuseum Schloss Kremsegg, Austria, collection Streitwieser)

The last crucial development in the evolution of the horn to its modern form was the invention of valves. In 1814 Heinrich Stölzel from Berlin presented a valved horn, and in 1818 he and Friedrich Blühmel were granted a patent for a piston valve. Since then the valve horn has undergone permanent improvements to its construction and sound, because the quality of the sound of the first valve horns was nowhere near as good as that of the natural hunting horns. It is for this reason that the valve horn was initially rejected – as was the valve trumpet later on – or used in the orchestra only in combination with the natural horn. Carl Maria von Weber (1786–1826), Richard Wagner (1813–1883) in his early works and Johannes Brahms (1833–1897) all preferred the sound of the natural horn. One of the first composers to write for the valve horn was Robert Schumann (1810–1856), who in 1849 wrote his Adagio and Allegro for horn in F and piano and his Concert piece for 4 horns and orchestra for the valve horn.

The structure of the modern valve horn is still basically that of the triple-valved horn, which emerged in 1830. It was the addition of the valves that gave the instrument a full chromatic range.

Toward the end of the 19th century the German instrument maker Fritz Kruspe produced the first double horn in F/Bb. From the middle of the 20th century this horn, equipped with rotary valves, gained greater acceptance than models with piston valves, and today the double horn in F/Bb is the most widely used horn in orchestral music. It is joined in most cases by horns in F, in high Bb and the triple horn in F/Bb/high f.