Elliot Bergman remembers his sister Natalie running around their family's kitchen in cowboy boots, belting out Mariah Carey tunes. She was 4. Nowadays they're known as the brother-sister duo Wild Belle, and their just-released first single, "Keep You," is a deliriously catchy confluence of organic electro and reggae, with Natalie's voice floating just above the drum beat. She possesses understated beauty: deep, quiet eyes and a tangled mane of slouching blond hair. Her brother, eight years her senior, is a scruffy Alex Ebert look-alike, quietly brooding and affable.