Modern militaries have marching bands. Their use, to the best of my knowledge, is to help troops keep a unified pace while marching. I think I remember reading somewhere that they [(snare) drums] were also used to help coordinate troup maneuvers during the time of line infantry battles (feel free to correct me here).
The use of "war drums", "war horns", etc. has become a staple of battle scenes in movies set at ancient times (and to a lesser extend medieval times). They are depicted to be used mostly by the move "savage" side of the battle, like Vikings, Picts, or any other "tribal" faction.
Is this depiction actually based on historical facts? Do we know if the ancient greeks used war drums to pump up their soldiers? Do we know Vikings, Picts, Scots, etc. used horns, badpipes, etc. prior and during the battle to intimidate the enemy and get ehri own men fired up? etc.
While my question is mainly aimed at the use of intruments for psychological battle-related purposes, if you have knowledge about other military-related use of intruments (signalling, keeping pace, facillitating maneuvres, etc.) during ancient and medieval times, please feel free to share - I'd be quite interessted in learning how the typical day/duty of a "musical specialist" in an ancient army would have looked like.
The ancient Greeks did not have war drums. They used the salpinx, a large trumpet, to sound the charge (and sometimes the retreat). Later Hellenistic infantry formations were capable of performing a number of manoeuvres based on salpinx signals. Here's a picture of a Greek warrior blowing one.
The only other musical instrument seen on Greek battlefields was the aulos, a double pipe that produces a very loud, piercing blare. The Spartans used aulos players to set the rhythm by which they marched. Since the Spartans were the only ones to march in step, the other Greeks did not really understand what the pipers were for, and never copied the practice.
To pump up the men in the battle line, the Greeks used their voices. They had the habit of singing a song called the paean before every battle, which was supposed to increase their spirit and sense of community. Different Greek peoples had their own version of the paean, but they all sang it just before the charge.