Nineteen-year-old Sierra Hull has been turning heads in the bluegrass world since she joined Alison Krauss on the Opry stage as a sixth-grade mandolin prodigy. Mentored by Krauss and now championed by Chris Thile, Hull fulfills the promise her stellar elders see in her on this, her second Rounder album. Where to start enumerating the wonders herein? Well, consider her hard driving instrumental, “Bombshell.” After executing a deft, rippling mandolin solo to kick things off, she returns to reassert herself dynamically in between aggressive solos by fiddler Stuart Duncan and guitarist Bryan Sutton, as Union Station’s Barry Bales (who also produced) keeps the bottom solid on bass. Or how about her singing? Her voice has a Krauss- like sweetness to it but its own spunky attitude, plus a newfound confidence, as she demonstrates in her sassy, western swing-styled kissoff number, “Best Buy,” and in the heart-tugging ache she brings to her lilting love ballad, “I’ll Always Be Waiting For You,” a devotional for the ages. If it’s not obvious from these highlights, she’s also developed into a first- rate songwriter. Producer Bales doesn’t gussy things up but rather fashions a rich, ensemble backdrop over which his young charge soars triumphant—clean, clear, and glory bound.