Familiarity breeds comedy in the Sirens' 50-minute show of short improvised scenes: instead of building on characters or narratives, the ten-woman group explores permutations of a single human relationship suggested by an audience member. At the show I saw, to-be, current, and former sisters-in-law were presented in love triangles, as estranged siblings, and at family yard sales. The interpersonal theme suits the players' personable style: they invent names for one another during scenes, closely bookend the stage if they're not performing, and punctuate the evening with anecdotes from real life. Together for seven years now with few changes in personnel, the Sirens have a great time--and that positive energy really rubs off. Through 6/30: Fri 10:30 PM, Playground Theater, 3209 N. Halsted, 773-509-6433, $8-$12.