A type of Musical Instrument that produces pitch by the players vibrating their lips into a conical mouthpiece. This differs from the assumed definition of a brass instrument being just an instrument made of brass. The designation 'brass' has nothing to do with what kind of material it is made of (many woodwinds are made of brass, while some brass instruments are made of other metals), and everything to do with sound production.
The first brass instruments were simply hollowed animal horns, used for communicating over long distances. These slowly progressed into similar instruments made of copper, zinc, lead, tin, gold or silver (Bronze age). These formed the bugles that are still used militarily today. But the bugle cannot play the full chromatic scale (12 notes) necessary to play real music, so valves and keys were added in the 18th century, thus creating the modern day instruments.
Modern day brass instruments include, but are not limited to the, trumpet, cornet, flugelhorn, French horn, mellophone, baritone, euphonium, trombone, sousaphone, tuba, and contrabass. Although all these different instruments have different sounds and ranges, the pitch in all of them is produced the same.
Many people disagree how exactly a brass instrument's unique sound is produced, but (as a brass player myself), I will explain how I play. The instrument is played with the air, and not the lips. This may not seem to make sense, but if you think about it, how could the lips vibrate without proper air? The air causes the lips to vibrate, thus making a buzz in the mouthpiece, which then reverberates through the horn, and making the sound. Players are told to 'blow through, not into, the horn to create a more open sound.
As I have said, it is the air that produces the sounds, but the lips are still very important. The setting of the lips and face muscles is called the embouchure in brass playing. The embouchure consists of all the muscles in the face that are used to play the horn. Without a properly set embouchure, air would escape out the side of the mouth or the cheeks would puff, causing the throat to close.
The biggest essential when playing a brass instrument is correct breathing. Using the syllable 'home' helps to drop the jaw and relax the throat. Always breathe from the bottom up, feeling the stomach expand, then the chest. Improper breathing is big problem with young brass players. Shallow breathing leads to playing with a closed throat, stopping the air and preventing higher pitches.
See also: Woodwind, String, Percussion