Square is the word for singer Michael Whelan’s big-band revue of old favorites by Cole Porter, Rodgers and Hart, Jerome Kern, and others. Dorky costumes, cheesy lighting, and unsurprising “surprises” don’t help. The real issue, however, is Whelan’s stolid if technically expert singing: his powerful sustained notes homogenize the music, especially a horribly unquirky rendition of “My Funny Valentine.” Singer Roberta Duchak is more sensitive rhythmically yet awfully bright and unsupple on the high notes. Director Marc Robin’s choreography is brusquely sexy, but of the two dancing “Fever-Pitch Girls” only fluid, pliant Ariane Dolan brings these grand old songs to life. Overall this is a show that plays things safe, with predictably mediocre results. Through 1/8: Wed-Thu 7:30 PM, Fri 8 PM, Sat 5:30 and 8:30 PM, Sun 3 PM. Mercury Theater, 3745 N. Southport, 773-325-1700. $38.50-$42.50.