On her 2008 debut, Duffy introduced herself as a Welsh ingenue with a retro-soul sensibility, with simple songs of heartbreak showing off her sweet, sandpaper-scuffed voice. The 26-year-old singer-songwriter expands her style and subject matter on her sophomore offering, “Endlessly,” but somehow the result isn’t as satisfying. With frothy 1980s and ’90s dance beats mixed in with more soulful fare, it feels unfocused, as though Duffy isn’t sure who she wants to be musically.