There were buglers in all branches of the military during the ACW, cavalry, artillery, and infantry. They were used to signal things like drills, roll calls, inspections, marches, halts, rests, strike tents, form lines, etc., all being communications from generals to the troops. There were also two dozen bugle calls for commands to skirmishers out in front of the main lines of the army. Many of the buglers, although not all, weren't officially eligible to be a soldier, many being teenagers, and there are records of some, even known by name, that were as young as 11 or 12, and they had to know all the calls, just like the adult buglers.