In part because of the inexpensiveness and flexibility of digital technology, the universe of independent singer-songwriters is constantly expanding. But in that universe, Neko Case is near the center. She is to many what she herself would call “the Man!” Her last CD, an often surreal and melodically inventive collection of songs called “Fox Confessor Brings the Flood,” rose to No. 54 on the Billboard chart and ended up selling 200,000 copies. And publications like Rolling Stone and Spin and The Stranger, along with a growing cadre of intense, often lovesick fans, have lionized Case’s singing voice as uniquely clear and powerful. It may not vibrate as much as she would like, but it’s not the angel-sweet sound of Alison Krauss, either — it has real richness and body. And on her new CD, “Middle Cyclone,” to be released in March by Anti- (a division of the punkish label Epitaph that features all their artists who aren’t punk), Case displays a wide vocal and emotional range only intermittently present on her six previous recordings and in her regular releases with the Canadian power-pop band the New Pornographers. She has often been described as a belter, a force of nature, a kind of vocal tornado. So this increased admixture of playfulness, delicacy and orchestral effects strikes you as the kind of variegation that artists — and species — make in order to survive and thrive.