The singer, who cowrote and sings on the Icona Pop hit "I Love It," played her first headlining U.S. show at a Making Time party in Philadelphia in March 2012.
"It was fantastic, really, really good," she remembers, talking on the phone as her tour bus makes its way to a show in Pittsburgh this week. "And then the next time I played there, there were five people in the audience. So I don't really know what to expect."
At a record store appearance in Chicago last week, she did a terrific synth-pop cover of the Backstreet Boys' "I Want It That Way," a video clip of which has since gone viral. "I knew the song, but I wasn't like a diehard fan or anything," she says of the boy band's 1999 hit, which was released when she was 7. "But I feel that that song is like a pop classic. It's emotionally dark. It's such an '80s song, really, at least the way I do it."
Most of Charli's musical cues are taken from the decade that preceded her birth. "I love that whole idea of dreamy romance, and a kind of drama in that period of time, when it comes to fashion and music and everything," she says of the Reagan-Thatcher decade. "I love Belinda Carlisle, the Cure. When we were beginning writing the record, that's what I was listening to. Martika's Toy Soldiers. Kate Bush. I guess it was kind of in my brain."
She began work on the album in 2011, but delayed its release for two years. "I was going to put it out when I was ready, because I'm the one who has to live with the record forever," she says. "I was growing up, being 18, 19, 20. It was finding out who you are, what you want to say, and what music you want to make. I needed it to be perfect."
And finally, the question everyone wants answered: What does the XCX stand for? "It was my MSN messenger name, which I guess is uncool. It was how I would sign off. 'Charli Kiss Charli Kiss.' "
When she was 14, "I started getting gigs at raves in London, and I didn't have a name. And the guy who contacted me was like, 'What do I call you?' And I said, 'Charli XCX.' "
Charli XCX, with Little Daylight, plays 8:30 p.m. Saturday at Union Transfer, 1024 Spring Garden St. Tickets: $15. Phone: 215-232-2100, www.utphilly.com.