The German playwright Bertolt Brecht wasn’t too impressed with the invention of the radio. “It was suddenly possible to say everything to everyone but,” he said in 1932, “when you thought about it, you had nothing to say.” He believed radio should be a realm of debate and political discourse, and that the listener should be part of the process. With Brecht as its springboard, “Radio-Activity” looks at other artists and collectives and their alternative communication initiatives, including textual and theatrical approaches. —E.C.