The TRUMPET was originally no more than an animal's horn fitted with a simple mouthpiece, and as such it had a natural military application in leading forces into battle. For this purpose and for similar ceremonial occasions, the fundamental limitation that the instrument could only provide a limited number of notes in a harmonic progression was no problem, but in the 13th century the development of the first folded trumpet heralded its gradual progression into the instrument we know today.
A big step forward in the 17th century was the introduction of crooks - lengths of tubing that could be inserted into the instriument to alter the pitch. The notes available were still from the harmonic series, but the player could for the first time 'crook' his instrument into almost any key he wanted, thereby providing much greater flexibility for the trumpet within an orchestral environment. Players during the time of Bach and Handel developed astonishing skills, but it was still hard work and - human nature being what it is - it wasn't long before players began to seek simpler ways of achieving their goals.
As a result, towards the end of the 18th century experimental instruments were produced with keys similar to those used on woodwind instruments. Haydn was so impressed that he composed his famous Trumpet Concerto (1796) for such a keyed instrument.
But it wasn't long before another major development occurred: the introduction of the valve trumpet with a complete chromatic compass. Three valves are connected to sections of tubing of different lengths; when pressed in various combinations, six lower notes each a semitone apart are obtained. The modern trumpet has a thin cylindrical bore for most of its length, widening over the last quarter into a flared bell. The common B flat instrument has a range of around three octaves above the E below middle C.
Various other instruments are in common use: the ones pitched in D and E flat are encountered most often. The smallest trumpet of all is the so-called 'piccolo B flat' which sounds an octave above the ordinary B flat instrument.
Mutes are used from time to time. A straight mute, shaped like a cone, gives a piercing and sinister sound; while a bucket mute makes the instrument sound more mellow. Cup and 'harmon' mutes are also used occasionally, producing soft and buzzy sounds respectively.