The young upstarts are cagey veterans now, heading into their tenth year of playing bluegrass — real bluegrass with Scruggs-style banjo, jaw-dropping mandolin breaks and taut and lonesome harmonies — the kind you expect from the founding generation of the style but rarely hear from the acoustic jam bands that only aspire to an opening slot at Wakarusa. Cumberland Gap's music is more rewarding: Led by the bluesy phrasing and modern songwriting flair of Greg Silsby, the band leans forward as one, focused and tight, and still takes chances with the American folk and country songbook, making covers of Hank Williams and Gordon Lightfoot wholly their own.