It’s called “The Power of Two,” but more than one duo is behind tonight’s power-duet cabaret at Arena Stage. For starters, there’s the pair of singers who are reuniting for what should be a beautiful evening, even if they don’t sing “Oh, What a Beautiful Mornin’.” The last time they harmonized at Arena, Nicholas Rodriguez and Eleasha Gamble were starring as lovers Curly and Laurey in the theater’s production of Oklahoma (shown). Now they’re back to sing a show arranged by two theaters, under the direction of two guys known for putting on blockbuster musicals at Signature Theatre. Matthew Gardiner, who helmed Dreamgirls and Xanadu, directs the cabaret, which will take place in Arena’s intimate Kogod Cradle. Gabriel Mangiante, Signature’s resident piano man, will play keyboards. The setlist features heavy tunes recorded by famous twosomes, including The Indigo Girls’ “Power of Two,” Marvin Gaye and Tammi Terrell’s “Ain’t No Mountain High Enough,” and “Anything You Can Do” from Annie Get Your Gun. Here’s predicting that last song will end in a draw. The show runs Dec. 11 to Dec. 15 at Arena Stage, 1101 6th St. SW. $25–$40. (202) 554-9066. arenastage.org.