In Which The Man Tries to Prevent Me from Being True to Mine Ownself

I have a particularly low voice for a girl. My friend Mike has a particularly high voice for a guy. We've agreed that he'd do quite well as a first alto, and I'd do quite well as a first tenor, so we decided to switch voice parts for the senior ensemble song. He chickened out, but I still learned the tenor part and have been singing as a tenor for the past few weeks (and blending far more easily into the tenor section than the alto section).

On Friday, our conductor finally figured out that I've been singing with the guys. He had an issue with that, and told me to go back to the alto part. So now our formation is thrown off, I need to relearn the song (I know both parts, but I keep on finding myself singing an alto-tenor hybrid part), and I stick out. The alto part for the song is in the break in my range, which means I have to sing loudly to get a decent tone, and there are some notes on which I can't change my tone much to match my section or I'll lose the pitch (or they could just sing darker like they're supposed to).

I'm considering sticking it to the man and singing the tenor part anyway. He didn't even notice I had switched parts from listening - he noticed when I filled a tenor slot in the formation. I blend so well as a tenor that it's nearly impossible to tell by ear that there's a girl singing with them. I don't see why he's so adamantly against me being a tenor for just one song. I'll have to talk with him about it. If he's still against it, I'll just be an alto. I see no reason to pick a fight with my conductor just to prove I can.