Maggie's Farm

drums were used to control formations of troops in combat, either to transmit orders or (at a slower cadence than in this vid) to keep troops moving forward as a cohesive mass at a steady pace while under fire. this was important in the days (before about 1850) when tactics revolved around the column or lines of troops. most of these battles were decided when the attackers or defenders broke and ran before the enemy reached bayonet point.

I think you've got it wrong. compare any Napoleonic era battle where the killing zone is a hundred yards and massing troops on the attack is the best option: attackers have a distinct advantage because at this short distance, they're under fire for only a few volleys and if they remain massed and organized, they will punch through the line.

but by the US Civil War the killing zone started at 900 yards and dispersing the attackers and advances were made by short rushes. defenders had a distinct advantage and massing troops was typically fatal.

what you're describing is fire and maneuver, tactics not developed until the 20th century. pick up a M1903, it has a magazine cut off switch that was used because doctrine of the day required deliberate aimed fire, meaning loading single cartridges from a cartridge pouch. firing off a magazine was a last resort tactic. while fire and maneuver is barely possible with a bolt action magazine rifle, it is impossible with a slow muzzle loading musket.

the fife drumsticks playing Scotland the Brave at 4.00 were very, very cool.