Erroneously called the french horn, the horn traces its ancestry to Germany. The modern double horn is a new addition to the orchestra, first emerging in the late 1800s in Germany. The instrument is pitched in two keys B-flat and F, and the use of the thumb trigger switches between the two "sides' of the instrument.
Despite having two fundamental pitches - F and B-flat, the horn is considered an F instrument. As such, written pitches sound a fifth lower than printed.
The horn, despite its extensive solo range, has a p ractical range of two octaves. This is due to the nature of the instrument. Low pitches are difficult to play, and often limited to players that specialize in playing in the absolute lowest range of the instrument. Likewise, some players specialize in playing in the highest range of the instrument. However, for practical purposes, it is best to stay within the staff when writing for horn.
The double horn is used significantly in film music, due to its robust timbre. It can be a powerful instrument when played in large sections of four (or eight).
Unlike the other brass instruments, it resides in the upper range of its overtone series. Young horn players often struggle identifying the partial they are playing and pitch accuracy is one of the major hurdles for the beginner. Therefore, horns are not as agile as trumpets, and fast runs are discouraged.
One notable technique used by horns is the "horn rip". The closer intervals of the overtone series allow a horn player to "rip" through these partials, often jumping from the octave below.
Although not as common, horn players also can play "stopped". By placing their hand further into the bell, the timbre of the horn is changed to a very brilliant tone. The pitch is actually raised a half-step, though the horn player is the one that does the transposing. As a player is playing against higher resistance, this can only be performed at louder dynamics.