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My director of bands is new to High School marching band. she has directed us for two years, and we are the first band she has attempted to direct. in the first year, she was great, allowing the proper ammount of authority to the drum major, while at the same time, accerting her authority as director.
this year, she has become a band natzi.

We are preparing for a parade in band latley, so, as you would expect, our drum major was conducting us and at a marching tempo. but, about a third of the way through practice, our director took the podium, and conducted the song WAY faster than a marching tempo. when our drum major, who has been in marching band FAR longer than the director, tried to correct her, and politly let her know that that was to fast to march in a parade, she blew up. she began yelling at the band about how "We marched faster than that in our 'pirates' field show" and "Its not that hard, i know marching, you can do it!"
she doesn't know what she is talking about and it is pissing us all off, but if we say anything, she will just explode.

what should we do?

I hate to say it, but ultimately, it is the band director's say. However, there are a few things you can do. I would especially get your drum major to talk to her - the drum major is the link between the band and the director. My suggestion would be to compromise - faster than your drum major is taking the tempo, slower than the director has. Band members can talk to her about this, but I'd try to get your DM to first. Most importantly, though, talk to her in private! Don't try to confront her during band. Talk to her outside of class, preferably where there aren't a bunch of band students around. This way, she won't feel as if you are trying to take away her authority with the rest of the band (hopefully). Point out to her that her tempo is a little fast to be marching for the entire duration of the parade. If she compares it to your Pirates field show or whatever, point out that in a show, you generally don't move 8 to 5 (8 steps for every five yards - standard step). Parade marching, you do. Sometimes you march bigger steps. A parade is long and tiring, even with cadences and everything. A fast tempo will make everything worse. A slower tempo, even with large strides to keep up with the rest of the parade, is much easier to maintain.