Shipwreck Singer

The last ability affects creatures that are already attacking when it resolves. Activating it before combat won't affect any creatures that attack later that turn.

The controller of each attacking creature still chooses which player or planeswalker that creature attacks.

If, during a player's declare attackers step, a creature is tapped, is affected by a spell or ability that says it can't attack, or hasn't been under that player's control continuously since the turn began (and doesn't have haste), then it doesn't attack. If there's a cost associated with having a creature attack, the player isn't forced to pay that cost, so it doesn't have to attack in that case either.