What is the purpose of a drummer boy?

Drummer boys were used in armies from the 17th to the 19th centuries, particularly within infantry and rifle regiments to issue commands as signals on the battlefield when verbal commands and bugle calls could not be heard over gunfire and battle noise.

Drummer boys also signaled the charge when troops moved ahead into combat; sounded assembly to alert scattered formations to gather together under their colors for movement and inspection; maintained cadence for marching; marked intervals of time while men lined up and readied their muskets before an assault upon fortifications and artillery lines; accompanied military funerals (as they still do); and conveyed the alarm if troops were ambushed while bivouacked at camp or night quarters