Donna Summer’s fourth consecutive double album in an infamous age of excess, On the Radio makes clearest how fully she and producer Giorgio Moroder owned the disco era. Studio 54 was only the most famous of the worldwide nightclubs spinning “Love to Love You Baby,” “Sunset People,” “Dim All the Lights,” “No More Tears (Enough Is Enough),” “Hot Stuff,” “Bad Girls” and the rest of Summer’s limitless hits. On the Radio boasts nearly all of them.