The first group of blown instruments, or aerophones used by the Romans, was the brass instruments, which were essentially hollow tubes played by the musician "buzzing" into a cup shaped mouthpiece. In many instances, these instruments were used for military applications, especially signaling and heralding. A few specimens of these metallic devices include the cornu, the buccina, the tuba and the lituus. In general, a tuba, which was four foot long pipe with a flare at the end, was used by foot soldiers for calls like those of a modern bugle. On the other hand, the buccina served the same purpose in a civilian setting, announcing changes of watch and processions. The cornu and the lituus, a small horn and a large curved horn respectively, were employed as signaling devices by heavily armored foot soldiers and cavalry.
Notice how the cornu and the buccina are very similar, but the cornu has a cylindrical bore while the buccina has a cylindrical bore.