The trumpet is one of the oldest musical instruments. Most ancient and medieval trumpets appear structurally similar to modern trumpets, though they lack valves and are not always coiled. Trumpets were just beginning to be used for music at the end of the Middle Ages. At this time, a few structural changes were made to them to make them more useful in a musical setting.
No medieval trumpets had valves or keys, giving these instruments a limited ability to change notes. In order to play different notes on this type of instrument, trumpeters would adjust their embouchure, tightening the lips to produce higher notes and loosening them to produce lower ones. Not all notes can be made through the use of embouchure alone so medieval trumpets were only able to play a series of harmonic overtones rather than the full chromatic scale that modern trumpets are able to play.
In their simplest form, medieval trumpets were shaped like long tubes with a wide end, called a bell, and a mouth piece that could cover the player's lips. These tubes were made out of metal sheets which were rolled into a cylindrical shape. The edges of the metal would be sealed so that no air could escape on its way from the mouthpiece to the bell.
These simple medieval trumpets could be anywhere from 1 foot (30 centimeters) long to longer than 10 feet (3 meters). Long trumpets needed to be balanced on stands or carried by many people when they were played. The difference in the length of these medieval trumpets affected the pitch of the instruments, with shorter instruments producing higher sounds and longer instruments producing lower ones. In medieval times, most trumpets were a length that made them easy for one person to carry because they were generally used for communication during battle.
Medieval trumpets were also often made into a coil. Coiling the tubing made it possible for longer, and thus lower pitched, trumpets to be easily held by one person. In most cases, the metal tube was coiled one or two times. This change in the shape of the trumpet does not affect the sound it produces.
Towards the end of medieval era, trumpets were being used in music as well as on the battlefield. Once these instruments were adopted for musical use, it became necessary for the player to be able to change the trumpet's key so that it could be used in different songs. Some medieval trumpets were made with removable tubing, or crooks, which could be traded with other pieces that were longer or shorter. These instruments were still only able to produce overtones, however, so their use was usually restricted to keeping rhythm.