The first question that should probably be answered is whether or not the Horn should be called a "French" Horn and whether indeed it has any connection with France and the French whatsoever. There is no definite answer to this and views on the matter tend to widely differ. According to this source, it is only in the United States, Canada and the United Kingdom that the horn is known as the "French" Horn and most european literature refers to the instrument simply as the "horn". This source states that the name for the instrument in the UK came from the fact that hunting horns differed greatly from England to France; while French hunting horns were large, worn over the shoulder, and looked roughly similar to what is now called simply a "hunting horn", British hunting horns were much smaller, held in a single hand and pitched significantly higher. To differentiate between what the British called a "horn" and the instrument that is nowdays called a horn, the larger modern instrument was given the prefix "French", as it reminded the British of the continental hunting horn. This source states that the "French Horn" was not developed in France, but in the Alps of the Germanic countries, commonly used to warn animal intruders who threatened the shepherd's flocks. The instrument, including the mouthpiece, was made entirely of wood and straw. Since the French dominated most of the Alpine region during the development of the horn the term "French Horn" became a popular term that has remained until today.

Of course the Horn didn’t start off in the form it has today. This is what it has evolved into to over a period of 27 centuries. It’s history can essentially be split into two periods. The pre 19th century period and the post 19th century period. The transition from one period to the other is marked by the introduction of the Valve into the design of the Horn. One of the earliest horn-like instruments, the lur, dates back to the sixth century B.C. The lur was made of bronze and was commonly used on battlefields by Scandinavian clans. It used to make a loud ugly sound perfect for what it was intended - terrorising enemy camps. The lur was nothing more than a long tube and the sound it made was a reflection of its simple form. This form remained until the 17th century when a more rounded form became popular in hunting.The fundamental structure of the 17th century horn and the modern day horn remains the same.

The Horn consists of four basic sections: the mouthpiece, a tapered mouthpipe, the cylindrical section and the bell with each part influencing the acoustical behaviour of the instrument. Like any brass instrument, is essentially a tube closed at one end - at the lips. When you blow into the instrument you compress the air immediately in front of the lips. When you stop blowing compression of the air also stops so you get a pattern of compressed and stretched regions of air or in physics jargon a series of compressions and rarefactions - a longitudinal wave. When the wave reaches the other end of the instrument it reflects and a standing wave is set up. This is just the basic formation of a standing wave!

But the standing wave immediately begins to die out as energy is dissipated at the walls of the tube or radiated as sound from the bell. In order to maintain the oscillation you have to continuously supply puffs of air and supply them at the appropriate time. Simply blowing into the instrument will not sustain the oscillation, in the same way that a steady force applied to a swing will not keep it in motion, because energy will be added during half the cycle and removed during the other half. To maintain the oscillation you must add air at the appropriate part of each cycle. That is when the mouthpiece pressure is high. It would be virtually impossible for the player to synchronize his or her lip opening by muscular action alone and fortunately this is not necessary. Pressure pulses reflected back from the horn force the player’s lips open at the right time during the cycle of oscillation. This is known as positive feedback. It is equivalent to having a pressure controlled valve that admits air whenever the pressure is high. But positive feedback only works if the oscillation frequency is above the natural resonance frequency of the lips. The natural resonance frequency of the lips is in turn determined by their mass and tension which can be altered by the player.

At the other end of the horn is the bell and while at one end the player and mouthpiece control the air that goes into the instrument, at the other end the bell controls the air that leaves the horn. It is known that the resonant frequencies of any tube closed at one end are given by f = nv/4L and for the Horn these frequencies are 23Hz, 69Hz, 114Hz, 161Hz, … odd multiples of the fundamental frequency of 23Hz. These resonant frequencies are precisely those frequencies of the standing waves than can be accommodated by the tube. The standing waves I’ve already mentioned are only possible if waves are reflected by the open end of the tube. However, at the same time, if the tube is to be musically useful energy must be radiated from the open end. There is therefore a conflict between the fact that air must be reflected for the standing wave to be formed but at the same time radiated for there to be sound and as strange as it may seem the horn (as is the case for all wind instruments) is designed to keep as much of the sound within the tube as possible. They are designed not to radiate sound. This is where the importance of the bell becomes apparent. Whether a wave will be reflected by the open end or radiated from it depends on the size of the wavelength of the standing wave and the diameter of the tube. If the wavelength of the standing wave is much longer than the diameter of the tube the energy is virtually imprisoned in the tube and little, if any, sound emanates from it. If however a bell is added to the end of the tube then the bell acts as a gradual increase in the diameter of the tube. However, the bell will only be effective if the diameter of the tube increases over a tube length equal to the wavelength of the sound.If the bell flares too abruptly then the sound wave is unaffected by the bell’s presence. So that’s why the bell of the horn is important.

On the historical front, as the aristocratic sport of hunting spread horn-makers experimented with various shapes and sizes to increase the range of possible notes. Once it was realised that changing the length of the horn made it possible to change the range of possible notes the horn began appearing in concert halls and theatres but was considered too harsh to be included amongst the oboes and violins and was used only in scenes depicting horror. During the Baroque period composers began writing much more melodic music for the horn but the fact remained that the horn was still just a single fixed length of tubing and its musical potential was limited to the natural harmonic series. If the player had to change keys he would have to change horns.

This of course was impractical and therefore led to the invention in the early 18th century of the crook. The crook was just an additional piece of coiled tubing that could be inserted into the horn to change the overall length of the instrument. Changing the length also changed the pitch so that the entire harmonic series could be played in a different key. Still, however, to change keys the player had to stop playing and change crooks. This delayed the player and it was a bit too much of an effort to carry around all of the necessary crooks. So by the 19th century another development came about - that of the valve.

In 1816 Heinrich Stflzel, a chamber musician from Pless in Upper Silesia, and a colleague of his, Friedrich Bl?mel, were granted a Prussian patent for the valve mechanism. The value mechanism is basically a mechanism by which lengths of additional tubing can easily be incorporated into the main length without the player having to make any alterations to the horn. To show the importance of this development I have an extract of what was in 1815 published in the Leipzig periodical Allgemeine Musikalische Zeitung:

"Heinrich Stflzel, the chamber musician from Pless in Upper Silesia, in order to perfect the Waldhorn (the german name for the horn), has succeeded in attaching a simple mechanism to the instrument, thanks to which he has obtained all the notes of the chromatic scale in a range of almost three octaves, with a good, strong and pure tone. All the artificial notes… are identical in sound to the natural notes and thus preserve the character of the Waldhorn. Any Waldhorn player will, with practice, be able to play on it. So that his invention may become more widely known and used, Herr Stflzel has laid his invention at the feet of His Majesty the King of Prussia and now awaits a favorable outcome."

So you can see that horn valves were a matter for the concern of Kings!

There are two types of valves. Piston valves and rotary valves. Historically the rotary valve is the successor of the piston valve and was invented by Joseph Riedl in Vienna.Both types work in the same way.

For the piston valve, in the raised position, a hole called the windway, simply extends the air column straight through the valve. For the rotary valve, when the valve is pressed two other windways connect the main air column to an additional length of tubing.

However there’s a problem in designing the lengths of tubing for each valve. The first valve lowers the pitch by a tone (2 semitones) and the second by a semitone. So it’s expected that pressing both valves together will lower the pitch by three semitones. This however isn’t the case.

Without considering the maths of why the lengths have the values they do, in order to lower the pitch by a whole tone the first valve must add a length of tubing 12.2% of the total length and in order to lower the pitch by a semitone the second valve must add a length of tubing 5.9% of the total length

By addition, pressing both valves adds a length of 18.1%. However, 3 semitones require an increase of 18.9%. Due to this discrepancy the additional lengths of tubing are not fixed. They are allowed to slide in order to compensate where necessary.

The final development in the horn, is the invention of the double horn. A full double Horn is essentially two complete horns built into one instrument with both horns sharing the same mouthpipe and bell. One of the horns is tuned to F and is thus called an F Horn and the other is tuned to B flat and thus called a B flat Horn. The purpose of the fourth valve is to switch between the two horns and it works in exactly the same way as the other valves (F Horn is longer). When the B flat horn is used the other 3 valves send air into the slides that are the correct length for the B-flat horn. When the F horn is used the same applies.