“The legion also has its tubicines, cornicines and buccinatores. The tubicen sounds the charge and the retreat. The cornicines are used only to regulate the motions of the colours; the tubicines serve when the soldiers are ordered out to any work without the colours; but in time of action, the tubicines and cornicines sound together. The classicum, which is a particular signal of the buccinatores or cornicines, is appropriated to the commander-in-chief and is used in the presence of the general, or at the execution of a soldier, as a mark of its being done by his authority. The ordinary guards and outposts are always mounted and relieved by the sound of the tubicen, who also directs the motions of the soldiers on working parties and on field days. The cornicines sound whenever the colours are to be struck or planted. These rules must be punctually observed in all exercises and reviews so that the soldiers may be ready to obey them in action without hesitation according to the general’s orders either to charge or halt, to pursue the enemy or to retire. For reason will convince us that what is necessary to be performed in the heat of action should constantly be practised in the leisure of peace.” (De Re Militari, Book II.)
Like the Greek salpinx the Roman trumpets were not regarded as musical instruments. Among the tems used to describe the tuba’s tone, for instance, were horribilis (“horrible”), terribilis (“terrible”), raucus (“raucous”), rudis (“coarse”), strepens (“noisy”) and stridulus (“shrieking”). When sounding their instruments, the tubicines sometimes girded their cheeks with the capistrum (“muzzle”) which aulos (“flute”) players used to prevent their cheeks from being puffed out unduly.
This is the type of signal music Daniel meant in his comment to Saturday's post. However, while these trumpets were not intended to produce music themselves during Roman times, they were both reappropriated for musical use by Bach's time, and of course were the inspiration for those crazy trumpet parts in Respighi's Pines of Rome. Here is a video that includes pictures and audio of the litui used in Bach's "O Jesu Christ, meins lebens licht":