Most principals avoid the band hall unless they were former band directors. It is very possible that your admin. is oblivious to what is going on between you and the HBD. Speak with the admin. that you trust the most ASAP, follow his advice, and go forward from there. The sooner you get to the admin. the better.
Keep your documentation in a professional journal. Since you are worried about validation, know that professional journals are admissible in court. Write down what he said/did, and when, and who was in the room at the time. Give a copy to your admin. prior to the conference the other poster mentioned. Of course the HBD is going to deny everything, but at the same time if this is an ongoing issue, you are going to have documented much more than one occurrence; more likely you will be documenting on a daily basis. The more you write down, the more difficult it will be for the HBD's denials to be taken seriously.
When you send out applications for next year, and when you interview, when they ask why you left this position, answer honestly..."Hostile Work Environment".