How about we just simplify it to "must maintain concentration", which will have the built-in effects of distraction due to damage? Like so?
Dancing Song (Su): Once per day a verru may sing a chiming tune that causes all creatures within 30 feet to dance uncontrollably. Affected creatures must succeed on a DC X Will save or suffer the effects of an irresistible dance spell. A veeru can sing a dancing song for up to 3 rounds, and must maintain concentration. Affected victims continue dancing for 1d4+1 rounds after the veeru stops singing. Dancing song is a sonic, mind-affecting compulsion and can be neutralized by a bard's countersong ability. The save DC is Charisma-based.