Hollywood versions of Broadway musicals pretty much died in the 1960s, the victims of changing musical tastes, bloated budgets, incompetence and audience indifference, and film executives know it. Oh, there have been successful adaptations of Broadway hits from time to time in the intervening 40 years, usually accomplished by filming a musical as if it were a straight drama with occasional musical interludes. Cabaret and Chicago are prime examples of this, films in which the characters never actually sing unless it’s a dream or a stage act. Notable exception: the ultra-cheesy film version of Grease, with its 30 year-old “high school students” and ’50’s camp, and the recent Dreamgirls, which succeeded by dumping almost the entire original score that was sung on Broadway. But Grease was 30 years ago, and Dreamgirls is a musical about pop music, like most of the musicals currently on Broadway, where the genre is also in the process of dying a slow death. The overwhelming majority of movies based on Broadway musical hits have bombed away: Hello Dolly, Man of La Mancha, Rent, Phantom of the Opera, A Chorus Line, The Best Little Whorehouse in Texas, Evita…all big and costly flops. Why? Most audience members under the age of 60 don’t like musicals very much (quick: what was the last pop hit that came from Broadway?), and regard characters singing their emotions as just plain silly.

A particularly unsuccessful vein has been the much-worshipped musicals of Stephen Sondheim. Beginning with the almost unwatchable A Funny Thing Happened on the Way to the Forum, no movie based on a Sondheim musical has been anything but box office poison. The film adaptation of his A Little Night Music is a contender for the title of worst Broadway musical film ever. So when someone at DreamWorks momentarily went nuts and green-lighted a Tim Burton adaptation of Sondheim’s most popular musical, the macabre and operatic Sweeney Todd, the studio was facing huge financial risks. How could the film draw the many fans of Johnny Depp (the non-singer star), the admirers of director Burton (who has never directed a live-actor musical), and slasher-flick junkies (Sweeney Todd is a throat-slitting serial killer) without tipping them off that they would be paying to see a (yuck!) movie musical?

Easy: fool them!

In the past, misrepresenting a film in its promotional campaign before release was (in addition to being dishonest and wrong) suicidal. A misled audience would buy the tickets to early showings, discover that it wasn’t what they expected or wanted, and then give the film terrible word-of-mouth, killing ticket sales. This is what happened in 1981, when Warners’ trailers and ads for its arty and grim musical drama Pennies from Heaven represented it as a wacky comedy in order to attract the young fans of its star, Steve Martin. But Pennies from Heaven wasn’t a comedy at all, and Steve Martin wasn’t funny in it or trying to be—his character is executed at the end of the film. Early audiences, expecting Martin to be wild and crazy, hated the movie, which became a box-office flop. But today movies make most of their money in the first weekend. By the time word of mouth gets around, the studio has taken in substantial receipts. In other words, it can pay to fool audiences if you can get enough of them to the theaters on that first weekend.

Clearly, this is DreamWorks’ plan. The TV trailers for Sweeney Todd do not show a single character singing, or give any hint that Sweeney Todd is a musical. The movie is presented as a straight thriller or horror movie. The longer theatrical trailer does include a brief moment showing Depp as Todd singing a phrase without musical accompaniment, which would only suggest (to someone unaware of Sweeney Todd‘s origins) that at some point Johnny Depp’s character sings a bit. Neither the trailer’s narration not any prominent graphic mentions that this is a film adaptation of the hit Stephen Sondheim musical. To the contrary, the trailer hides this fact.

DreamWorks is playing the bait-and-switch con. It is unacceptable, a strategy indistinguishable from false advertising, bordering on fraud. The Scoreboard knows the defense in advance: trailers always misrepresent films, and audiences know it. The most effective form of misrepresentation is the most familiar: a lousy movie is made to look great by a well-edited trailer that packages the highlights skillfully. But the promotion of Sweeney Todd goes far beyond that.

It is unethical to present a movie starring Pauly Shore as a Tom Cruise film. You cannot ethically make a movie about hedge funds and advertise it as a Star Wars sequel. What makes a film “good” or “bad” is open to debate, but matters such a movie’s stars and genre are material facts that a film maker must not conceal. Dream Works has crossed the line by hiding the fact that Sweeney Todd is a movie version of a Stephen Sondheim musical. Burton is a talented director, and Depp has surprised us before; maybe together they can pull off the rare feat of creating a commercially successful movie musical. But if they are going to do it, they should have to do it honestly, and not by tricking musical-hating audience members into inflating the opening weekend’s receipts.