I'm not sure I understand what's happened, I can only tell you how I work.

On the few occasions when I do a commissioned projects (as opposed to "just" lighting camera) I always have a contract, even with friends. It doesn't have to be a twenty page legal document, a paragraph will do. With friends I usually use the excuse that it's to cover me insurance-wise if anything gets broken as my gear is only covered when I'm working "professionally".

The way I understand your position is that the band "allowed" you to film them in return for a dvd. Seems like they got the better deal, especially if they're unknowns. If that's the case then there's a bit of a Mexican Standoff. Neither of you can use the others' material without consent.

I suggest that you write up a simple document for the manager to sign, basically laying out what you expect them to do and what you will do in return. Keep it simple, documents don't have to be written in legalese to be valid.

For the future though, you've fallen into the semi-pro trap. All projects should either fall into the "amateur" camp or the "professional" bracket, half-baked schemes rarely work.