Nicole Atkins is one of those songwriters whose music almost defies classification; she’s been compared to everyone from Roy Orbison and Loretta Lynn to Kurt Weill and even Bruce Springsteen. (Well, maybe that last one is because she’s from New Jersey.) A true indie artist, her most recent album, January’s Slow Phaser, was made possible through crowd-funding and released through her own record label. You can hear Atkins’ genre-busting sound when she performs at the Emelin Theatre in Mamaroneck on April 26.