How do I get the band to respect my authority as P/M?

Earn it.

You are probably dealing with volunteers. You need to understand their motivations and goals. Your best bet is to focus your energies on the objectives (short and long term) that the membership has agreed to. Your fellow members will help you if they can see that you are working toward accomplishing their goals.

If you can form a "team", you'll have something to be very proud of.