Ask Lesley Roy to reflect on the motivation behind her music, and it becomes clear why the 21-year-old Balbriggan, Ireland, native has a voice and a presence that belie her relatively short time on this planet. “I’m a pretty simple, down-to-earth person, in that I live for my music and work really hard for it,” she begins, brogue well intact despite the fact that she’s called New York City home for much of the past year.