Dan Aykroyd is set to join Michael Douglas and Matt Damon in Steven Soderbergh’s HBO Films’ “Behind the Candelabra,” which follows flamboyant musician Liberace.Douglas stars as the famed performer, while Damon plays his live-in lover, Scott Thorson, whose memoir “My Life With Liberace” serves as the basis for the project. Aykroyd will play Seymour Heller, Liberace’s long-time manager who disapproved of his relationship with Thorson. Richard LaGravenese wrote the script. Gregory Jacobs and Susan Ekins will produce, while Jerry Weintraub will exec produce. Project was initially developed as a feature at Warner Bros. but when it couldn’t get any traction, the filmmakers determined the best way for the pic to reach a wide audience was via HBO. After debuting on the pay cabler, “Candelabra” will get a theatrical release outside the U.S. and Canada. Plan is for HBO Enterprises to sell the pic to independent distributors. Production is set to begin this summer. Aykroyd, who hasn’t appeared in a movie since the 2008 pic “War Inc.,” recently wrapped Jay Roach’s political comedy “The Campaign.” He’s repped by CAA.