1. History of French Horn

The leader of the brass section is the French horn. But when it was first made nobody used it indoors because it sound harsh. In France the nobility used the horn during hunts and made up special codes to signal each other. It was even used by the night watch to call when there was trouble.
Even though it is called the French horn it first began to be developed in Germany. It was completed as we know it today in France. So that's why we call it a French horn. Some French horns are really two horns in one. They have two sets of tubing. The player switches between  the two sets of coiled tubing by working a valve with his left thumb. One set of tubing gives a mellow, rich, deep tone. And the other makes a higher, brighter sound.
Once the French horn became part of the orchestra its shape began to change. The tube got longer, the bell was made wider, and it got its crooks and valves. It is the only brass instrument with a funnel-shaped mouthpiece. If all of the tubing were uncoiled it would be over 20 feet long.
The valves of a French horn are rotary valves. When the player pushes down on a valve it pulls a string that opens or closes different valves. French horn players put their right hand inside the bell of the horn to adjust the tone.

2. Select a French Horn

Due to its complex manufacture and the huge amount of labor required to construct a French horn, it is one of the more expensive orchestral instruments. This makes it especially important that you select the right instrument for your needs. Here are a few pointers on the basic differences between various models and their pros and cons.

Single horns
French horns (known simply as "horns" in non-English speaking countries) come in two basic types: single horns and double horns. Single horns come in two keys: F and Bb. Each type of single horn features three rotary valves. The F horn (for the key of F, not an abbreviation of "French") is the most popular single horn for students in the U.S. For larger beginners, a double horn is preferable since most students will move to a double horn anyway within a year or two. A single horn is sometimes preferred for younger beginners because of its smaller size, lighter weight, and smaller price tag.

Double horns
Through the wizardry of tubular engineering, a double horn is actually capable of shifting between the key of F and the key of Bb through the use of a fourth valve. Actuated by the left thumb, this valve actually cuts out about four feet of tubing from the vibrating air column within the horn. Some horns can be changed so that the lever works the other way around, turning the horn into an F instrument when engaged.

That's a wrap
A: A French horn is simply a very long tube that is coiled up to make it portable and is fitted with valves to lengthen or shorten the air column by rerouting it. The specific design of this coiling is called the "wrap." There are three basic types of wrap. The Kruspe wrap locates the fourth rotor valve above the other three when the horn is in playing position. This makes for a shorter linkage between the finger key that actuates the fourth valve and the actual valve.
The Geyer wrap (which-like the Kruspe wrap-is named for its German designer) locates the fourth rotor valve below the other three. Since the linkage reaches past the other three valves, it is much longer.

The child's wrap, children's wrap, or 3/4 wrap is a student single French horn that is coiled very tightly to make it easier for a child to handle. The vibrating air column is the same length, just in a smaller package.

 

Rotor linkage - string and mechanical

B: The valves that vary the length of the vibrating air column in a French horn work by rotation. The valves comprise thick disks with holes drilled through them that rotate to connect various tubes to one another. These disks are well below the finger keys that control their rotation. The keys are connected to the valves either by super-strong string or by metal rods (mechanical linkage).

String linkages are very quiet in operation but eventually the string can break and need to be replaced. It is the most popular type of linkage in the U.S. Europeans tend to prefer the mechanical linkage because it never needs replacement, though it can sometimes be heard during quieter passages.

Bell throat size
The throat of the bell is the area where the hand is placed while playing. A smaller throat makes it easier to control the tone, but the timbre will be thinner and less resonant. A larger throat size provides a more open, full-bodied sound, but is more difficult to control.

Bell and first branch material
Any serious player can tell you—and scientific research has verified—that differing materials used in the bell and the first branch (what the bell attaches to) make a significant difference in the instrument's tone. Yellow brass produces a bright tone (accentuating the treble end of the spectrum) and has a very snappy response. Rose brass, also called red brass or gold brass, produces a darker tone with a little bit less-defined response. Nickel silver produces the darkest tone.

Players from different regions, which are associated with slightly different playing styles, tend to choose different throat-size/metal combinations. For example, Los Angeles and New York players often select a large-throated, nickel horn; while Chicago players usually prefer a medium or small-throated horn with yellow or rose brass bell.

Screw bell
C: Many French horns come with a bell that can be detached by twisting it off the first branch. This is called a screw bell or detachable bell and allows the horn to fit into a smaller case for easier transport. There are no significant drawbacks to this design, and it's a very popular option.

3. Parts

A French horn is made of tubing, valves, levers to operate the valves and a mouthpiece. The individual tubes can be moved to adjust pitch. Additionally, the tubing has a large, flared bell that the right hand fits into to change the pitch and sound. The left hand operates the levers to change the notes.

4.Types of Metal

Beginners' horns are made from brass. Most commonly, they are made from yellow brass, which has a bright sound. Yellow brass is generally 70 percent copper and 30 percent zinc. Less frequently, French horns are made from gold brass or red brass, both of which have more copper. There are also nickel silver horns, which are generally 70 percent copper, 20 percent zinc and 10 percent nickel. Nickel makes the instrument stronger. Many French horns use more than one type of brass because the instrument has many parts.

5. Types of Linkage

The levers operate the valves by "linkage," which can be made of string or metal arms. String linkage is quieter but may break or need adjustment. Mechanical linkage may make clicking noises, but it lasts much longer.

6. Finishes

A French horn may be silver-plated or lacquered with an epoxy finish. Generally, beginners' instruments are silver-plated.