Not sure about written agreements. I started shooting rock bands in the early 1970's and then in 1976 for a record company, since I started I've never even seen a contract.
However when I've had backstage passes or been on the official guest list (as a photographer) I've always made a point of showing and offering images.
There is a kind of implicit agreement, if you're given certain privileges you should at least ask if your images are going to be used in a commercial way.
More recently the boot has been on both feet as I was a director of a record label, and I had to try and make sure the bands only used the best possible images of themselves in their publicity etc.
Photographing bands is hard work and the hours are often unsocial, particularly if you work 9-5 as well. For example this April I'll photograph 30 rock bands live on stage, as well as a location shoot with each band. Finding 30 different locations or settings is bad enough, let alone relying on the British weather. So there's no contract, no verbal agreement, just an imlicit understanding the record company and the bands will get the images I think they need, I have been working with the director of music since the late 70's though.
At the end of the day it is also about your own reputation, and you don't get repeat work is you abuse situations.
Ian
