He loves one of them, but doesn't know which one!

Manhattan Moon

Night club owner Dan Moore is trying to collect a debt owed to him by playboy Reggie Van Dorn, but Reggie is a playboy with no money but lots of social connections. In lieu of the cash, Dan gets Reggie to introduce him to the swells of high society. They go to the opera and, after hearing Yvonne Malloy sing, Dan falls in love with her. Reggie introduces them, but the introduction is to Yvonne's double and stand-in, Toots. This leads to many complications for all concerned.