Drummers were the communications core of the Civil War army. When an order was given on the battlefield a special drum beat was given out so that the junior officers and troops knew what to do over the din of battle.
Considered junior officers themselves, the drums were the morale of the regiment. Soldiers would listen for the drums to call them to action, keep them in step on the march, and let them know when to retire from the enemy.
To be a drummer in today’s regiment you don’t need to read sheet music - but a good sense of rhythm is always helpful!