Forgive me if this is condescending, but "contemporary" is "at the same time as now" whereas "contemporaneous" is "at the same time as events." At least, in the legal world it is. I have seen the distinction in historical texts too.
Thus, for example, Hitler's contemporaries would have left contemporaneous accounts.
Not at all. Advice and a little help with my education is welcome. I hadn't realized the difference. Maybe now I'll get somewhere.