nerves

When I'm singing by myself I seem to have almost everything down, when I sing in front of an audience my mix tends to hide and go away. Any tips?

Gavin! That can happen. Are you warming up before you sing in front of your audience? If not

do some deep breathing and stretching. Good warm up exercies to help with that head/mixed voice would be the Goog we talked about in previous chats. Goog is a good warm exercise for mixed voice. Keep up the hard work Gavin! 

Definitely warm up and find your mix prior to your performance, as Jim suggests. I've run into this when singing live and "pushing" for volume. If you're oversinging and "muscling into" your chest voice more than normal, mix can be hard to find (since it requires thinner, more precise coordination).