Richard Linklater is back at the Berlinale 11 years after he won the Silver Bear prize for his Oscar-winning “Boyhood,” this time with “Blue Moon,” a wistful chamber piece set on the opening night of Richard Rodgers and Oscar Hammerstein’s “Oklahoma!” in 1943. But the period comedy, which premieres in competition tonight at the festival, assumes the perspective of Lorenz Hart, the great American lyricist who was one half of Rodgers and Hart before a creative split.

The film takes place in or around the same bar at Sardi’s, where Rodgers (Andrew Scott) is greeting his rapturous public after the musical’s Broadway premiere while trying to keep a distance from his former creative collaborator, whose boozing and insecurities (and often wild overconfidence) make people uncomfortable. Ethan Hawke undergoes a unique physical transformation to give a theatrical but never overplayed performance as a five-foot-tall, sexually ambiguous alcoholic perched precariously on the wagon.