Taking her cue from Charlarn, the mermaid with the harp begins to sing in anticipation of the coming battle. Her song fills you all with marshall vigor, providing a boost to morale similar to Charlarn's bless spell.
While she sings (and for 5 rounds thereafter) the adventurers and all the merfolk will gain a +1 morale bonus to attacks, weapon damage rolls, and saving throws v. charm or fear. unfortunately, it won't stack with the bless.
[Initiatives please. Each character can spend two rounds preparing before round 1.]