The 10-member a cappella group Straight No Chaser demonstrates on its latest release, “With a Twist,” that the first ingredient in successful voices-only interpretation of instrumented pop is top-notch vocal talent. The singers master the tuning and blend demanded by their arrangements, which thankfully give precedence to the harmonic strengths of the human voice over instrumental mimicry. But they occasionally gravitate to a well-rehearsed sheen that feels overstylized, as heard on “Under the Bridge.” The set succumbs a bit too comfortably to a cappella conventions: Songs like Soft Cell‘s “Tainted Love” and Crowded House‘s “Don’t Dream It’s Over” have been turned inside out by college a cappella groups for decades. Adding “Single Ladies (Put a Ring on It)” as an interlude to the song “You & Me & the Bottle Makes Three” follows a pattern long leaned on to keep co-eds swooning. Production effects used to pump up the instrument-free resonance may result in a veneer that cools the voices’ natural warmth, but Straight No Chaser’s talent should be bound for a summer sales boon.