Prodigious professionalism is no substitute for a heartfelt performance. There’s something uncomfortably chilly about the few dozen chorus members in “42nd Street,” who don’t blink while they mechanically go through their dances like a bevy of mannequins possessed by the spirit of Ginger Rodgers’ legs. It’s as if they each have a personal Mama Rose them beseeching from the audience to “smile bigger!” and “kick higher!”

“42nd Street,” currently on at the National Theatre, is closer to a revue than a real musical; the story could sit atop the head of a pin. The acting is primarily vaudevillian and the production values – garish as they are – imply rather than transport.

To summarize, Dorothy Brock has been hired to add her star to brighten the dimming careers of playwrights Maggie Jones and Burt Berry and director Julian Marsh. Their musical “Pretty Lady” is a last shout – it will either make or break them. Brock (naturally) breaks her leg, hobbling their show. Enter the green, starving actress Peggy Sawyer, who saves the day.

Blair Ross plays Dorothy Brock, the aging, maladroit leading lady. Though she’s game for the role, the results are mixed: her comic timing is fine, even if it is restrained at times. Her best moments are during a shadow dancing number, though the footlights and staging are responsible for a major part of the effect.

Patrick Ryan Sullivan comes tantalizingly close to exacting a glimmer of truth out of his character, the director of “Pretty Lady.” He starts out gruff but suave, with a pinstripe suit and carefully pomaded hair that would impress F. Scott Fitzgerald. As his show starts to come apart at the seams, his clothes also seem to rumple and he lets his hair muss into a knotty coif.

As is superstition in show business, when vacating a theatre, a ghost light is planted onstage after the last dancer has taken her final bow so as to ward off the unwanted apparitions of dead theater folk who might haunt a production. It’s a legendary custom dating back to the early days of vaudeville. One almost hopes for a couple of those mythical phantasms to show up and give this show a little more spirit.

“42nd Street” is showing at the National Theatre at 1321 Pennsylvania Ave. through Tuesday, April 15.