Zambar starts a magical drum rhtym that fiercly boosts morale of his allies even having magical effects on them, preparing himself and his allies for battle every second allies in aoe range get attack speed, ms boost and portion of extra health for a period of time, if enemy hero is slain while Zambar is using his ulti the effect doubles.
If he is interrupted while channeling battle drums the effects remain where they were upon interruption.
Hmmm... drums.... let me through out a few ideas, since the OP is still incomplete right now
Cadence: Increase the marching (movement speed) of all units in an AOE / or cause all creeps (ally/enemy/neutral) and Heroes (Ally/Enemy) to follow (non-aggressively) the drummer
Rim Shot: Causes deafness (silence foes) in an AOE
Neil Peart: Cause all in AOE to fall and worship the drummer (AOE Stun)