SIERRA HULL When Sierra Hull walks on stage, there's a moment you might think she's just another cute Americana songstress - until she picks up a mandolin. The 20-year-old string prodigy makes tearing through intricate bluegrass arrangements look like child's play - and, for Hull, it was. She first caught Alison Krauss' eye at age 11 and has since shared the stage with a who's who of the folk elite. Now at the helm of her own band, the petite beauty single-handedly challenges any notion that high-energy bluegrass picking is scruffy guy territory. Just wait until she unleashes on that mandolin. $16. The Evening Muse.