I can tell you a bit about how copyrights work for software development. It seems like book and music copyrights should be similar, but I can't swear to that.

The copyright belongs to the programmer/author except in two cases. First, if there is a written agreement saying the work belongs to a party other than the author then it belongs to the named party. Second, if the programmer/author is a full-time employee then stuff written on the job belongs to his/her employer. This is called the Work-For-Hire Doctrine.

Let's say I hire a bloke as a contract programmer to write some software for me. The software belongs to him unless I have written agreement that says it belongs to me. Otherwise it belongs to him because the he's not a full-time employee.

It would be interesting to look at the Lomaxs' contract. Was there a written agreement that assigned ownership of their work? Were they were full-time federal employees with benefits and all, or just contractors?

One more icky detail: copyright laws rewritten in the 1970s and get updated all the time. The Lomaxs may have been working under different rules. Hope this is of some help.