The exquisite vocalist Kendra Shank and her friend and mentor Abbey Lincoln have both released new records this year, each comprising selections from Lincoln's body of thoroughly distinctive work. Comparing the two is instructive, as here the student outshines the master. On Abbey Sings Abbey Lincoln restyles her compositions in an Americana mode that would suit Cassandra Wilson or Norah Jones; but Shank's A Spirit Free (Challenge) uses inventive rhythm arrangements and a pilgrim's fervor to charge them with fresh urgency and cast new light on their lyrical wisdom. It's the singer, however, not those songs, that makes this rare Chicago appearance a must-see. On her four albums to date, but especially in person, Shank exudes an uncommon maturity. Her incisive phrasing lets her pierce the surface of her black-cherry voice and expose the textures within; she seems to reveal certain truths about herself and her material and to hint at more. For the first time she'll bring to Chicago her regular accompanying trio, led by pianist Frank Kimbrough, who combines a cerebral approach with an unconventional soulfulness. See also Saturday. a 9 PM, Green Mill, 4802 N. Broadway, 773-878-5552, $12.