Musicians of Chris Thile’s caliber don’t often give bad performances, but they do occasionally give exceptional ones. The Punch Brothers’ Spoleto 2009 performance at the College of Charleston Cistern proved one of those occasions. As dusk settled in amidst the Spanish moss-draped courtyard, the classical/bluegrass quintet excitedly offered a full sampling of their range, from their 43-minute heartbreak/rebirth opera “The Blind Leaving the Blind” to the White Stripes’ “Dead Leaves and Dirty Ground.” But the jaw-dropping highlight? Their haunting encore take on Radiohead’s “Packt Like Sardines in a Crushd Tin Box,” made all-the-more hypnotic by the rendition’s unplugged instrumentation.