You could make it that simple if you want, but it shouldn't be. A commercial license should be a stand-alone document specific to that situation. It should spell out what the other party is allowed to do with the image(s): Can they edit them, crop them, use them in print, on-line only, how many times can they use the image, for how long a period can they use the image, etc, etc. It should also detail what you can do with the image: You want to use it/them in your portfolio, you may want to retain commercial use so that you can sell it to/on stock sites, etc.
My use license (this isn't actually a release, you're licensing the image to them for use) would read along these lines:
In consideration of the sum of <amount they're paying you; if it's nothing use a token $1.00> <Your DBA/Name> hereby grants non-exclusive licence to <the musician/agent> to use the image <description of image, copy attached> taken at <location> on <date> of <name of person in image> for a period of <how long they can use it for>. <The musician/agent's name> may use the image in both (or specify which) electronic and print form in a size not to exceed <dimensions>. <The musician/agent's name> agrees that they will not edit or revise the image in any way except for minor cropping without first obtaining written permission. <The musician/agent's name> agrees that use of the image will be limited to XXX thousand occurrences at any one time.
<The musician/agent's name> acknowledges that <you> retains copyright to the images and the right to use them in any lawful manner.
All of the unknowns would be spelled out in detail, and the document would likely run to at least one full page. It's very common for people like this to try and take advantage of those new to the industry by having them "sign over" all rights to a potentially valuable image. At the end of the day, the artist is going to make money with this image. Why shouldn't you? It's your image!