Good morning! It sounds as if there is no room for negotiation with your husband on this... but if you can open up another discussion on the subject, I might suggest that you tell him that you know that he is fearful for her safety and feels responsible to protect her. It can be very difficult for a father to let go of his need to keep a daughter safe, but quite possibly there can be a plan designed to make them both happy.
Is it possible that a contract is drawn up between them which outlines the behaviors that if she demonstrates at this concert, will limit her privileges in the six months to follow? Such as: any under-age drinking, drugs, etc... If they both sign it, and if you tell her this is her final chance to prove that she is responsible or you cannot allow her to make her own choices for the next 6 months.
Teenagers need to have power and the ability to learn from their mistakes, as well as the trust of their parents. I truly hope that your husband is willing to compromise, because we ALL make faulty decisions while growing up, but the purpose is to learn from them and do better the next time. I wish you the very best!