So you thought backstage drama was the special province of theater folk? No, in Michael Holliger's new drama, Opus, it's a string quartet that becomes frayed in the rehearsal room — on the eve of the sleek ensemble's televised White House debut. Charlotte Shakespeare and director Matt Cosper renew a collaboration that began outdoors this past summer on The Green with The Tempest, taking this high-strung fracas to Duke Energy Theatre through Oct. 27. CharShakes isn't only demonstrating allegiance to the audacious Cosper but also to the playwright, whose Incorruptible was a holy success almost two years ago. Delivering the sex, drugs and barcarolle as members of the fractious Lazara String Quartet are James K. Flynn, Gretchen McGinty, Rob Kahn and CharShakes co-founder Joe Copley.