Despite being handicapped by a complete absence of CGI natural disasters, murderous firearms, or human bloodshed, the feature film “A Late Quartet” is surprisingly interesting. You could say it’s an adult film — about four adults (members of a world-famous string quartet) playing adult music (Beethoven, Shostakovich), grappling with adult concerns (mortality, fidelity, honesty). Writer-director Yaron Silberman isn’t afraid of big ideas or small idiosyncracies. Working with a masterful cast that includes Philip Seymour Hoffmann, Christopher Walken, Catherine Keener, and the sensationally sexy Imogen Poots, he’s made a movie as compulsively watchable as much louder films. Encore, we say.