If you've never seen The Third Man, (1) why haven't you? and (2) prepare yourself. Masterfully directed by Carol Reed from an original story by Graham Greene, the film features great performances by Joseph Cotten, Orson Welles, Trevor Howard and Alida Valli. Harry Lime's first appearance is one of cinema's greatest character introductions, and the film's sewers-of-Vienna climax is legendary. But the contribution that stands out most to first-time viewers is the score, composed and performed solely and entirely on the zither by a Viennese musician named Anton Karas. It is striking, unnerving, even a little off-putting at first. But by the third or fourth time you've seen The Third Man — and you will see it again — you'll wonder why more films aren't scored on zithers. It screens at 7 p.m. as part of the Best of the British Noir series at Tivoli Cinemas (4050 Pennsylvania, 816-561-5222). See tivolikc.com for details.