Duly noted

The stars of Nine all legitimately exercise their personal vocal chords. But in movie musical history, the voice and the vocalist haven't always inhabited the same body. Unspeakable? asks Kimberly Gadette – or merely a "mute" point?

Is it the song or the singer? Carrying a tune is fine, but it's the all-important carrying of the box office that resonates.

When Hollywood's leading men appear in movie musicals, it doesn't matter if the sound of music is drowned out by the roar of the crowd – as long as it's a roar of approval. (In some instances, if said leading man happens to be drowned out, all the better. Pierce Brosnan in Mamma Mia! anyone?)

The casting of non-singer Daniel Day-Lewis as the central figure of Guido Contini in this year's musical extravaganza, Nine, is far from an earth-shaking – or shall we say glass-shattering – precedent. Who could forget (scratch that, you probably have) Clint Eastwood in Paint Your Wagon? Looking back, Eastwood has stated, "I vowed I'd never do that again." Or his singin' sidekick, Lee Marvin? Streisand may not have been the prettiest choice for Hello, Dolly, but next to her croaking co-lead, Walter Matthau, she was a veritable screen goddess.

In the 2007 Sweeney Todd, we witnessed Johnny Depp attempting to warble the tunes written by Stephen Sondheim, perhaps the most challenging and complex composer/lyricist that the musical theater has ever known. But if a consummate performer like Depp can embrace a character, half-speaking, half-singing his songs as monologues rather than arias, then the actor can get away with vocal murder.

The movie musical canon is rife with examples of actors who disappear into their roles so completely that any vocal limitations work for them, making them seem more human, more believable. We can't think of My Fair Lady without recalling Rex Harrison's erudite professor over-pronouncing, rather than singing, every word. In The King and I, Yul Brynner's King of Siam is confounded by the English language, his halting sprecht-singing maligning every lyric – just as Oscar Hammerstein II intended. Even Chicago's Billy Flynn, as speed-mouthed by Richard Gere, is more swindler than singer. Without breaking a sweat, he bamboozles us into appreciating his verbal performance, no matter his level of actual vocal skill.

But the concept of shoehorning the popular movie star of the day into a cinematic remake of the latest Broadway hit doesn't always work: in Guys and Dolls, pairing a crooning Frank Sinatra with an ill-at-ease Marlon Brando was sheer disaster.

Mr. Brando's debacle aside, it's the women of the musical theater who've had a much harder time leaping from stage to the silver-throated screen.

More often than not, the job description for the film musical's leading lady included such adjectives as "gorgeous," "winsome," "charismatic," "beautiful," etc. If she could also sing? Brava. If not, then in the heyday of the Hollywood musical, a call was made to Marni Nixon, the "Voice of Hollywood."

Nixon has been behind the microphone for Audrey Hepburn's Eliza (My Fair Lady), Natalie Wood's Maria (West Side Story) and Deborah Kerr's Anna (The King and I). And even though Marilyn Monroe sang most of "Diamonds are a Girl's Best Friend" in Gentlemen Prefer Blondes, the producers turned to Nixon to hit Monroe's high notes. (Specifically the lyric, "those rocks don't lose their shape.")

With all this subbing and dubbing, a number of ironies were bound to abound. Such as the fact that although West Side Story is one of the most beloved musicals of all time, only one of the five leads, George Chakiris, actually sang his own part. (Though Rita Moreno could sing, the low notes gave her trouble and were sung instead by Lisa Kirk.) This must have killed Chita Rivera, the original Anita, who wasn't quite as screen-scenic as Ms. Moreno. And speaking of scenic, only the most rabid of Ethel Merman fans questioned why Gypsy's filmmakers ultimately chose Rosalind Russell (also dubbed) to star as the film version of Mama Rose.

When Julie Andrews didn't make the cut for the screen version of My Fair Lady – the part that she originated on Broadway – the Academy felt enough of an obligatory twinge to award her with an apologetic Oscar for, of all things, Mary Poppins.

Some spoonful of sugar.

But in the following year, the showbiz shoe ultimately landed on the other foot: though the original Maria of the stage version of The Sound of Music was Mary Martin, it was Julie Andrews, now the better box office bet, who switched roles from the injured to the injuring party. And in our collective memory, it will always be Andrews who serenades those hills that are probably, even at this late date, still alive.

An interesting coda: Andrews may have been the film star of The Sound of Music, but Martin received co-producing credit. And as co-producer of this particular box office smash, Martin earned approximately $8 million. As for Andrews, she got her upfront fee of $225,000 and a lovely "thank you." This time, it was Martin who snatched the sugar.

However, Martin lost in yet another leap from stage to film: her Tony Award-winning role of Nellie Forbush was reassigned to the younger, prettier Mitzi Gaynor. But given that Martin was twenty years older than Gaynor, along with the fact that a face is akin to the size of the Hindenburg once blown up by gigantic Cinemascope proportions, the filmmakers had to cast a female romantic lead who didn't look to have wrinkles reminiscent of twisting ravines raging through Bali Ha'i.

Of all the film dubbing ironies, it's the 1952 Singin' in the Rain that gets top prize. A Hollywood musical that parodies the leap from silent film to the talkies in 1930, Jean Hagen plays a glamorous silent film star who loses every shred of glamour once she opens her mouth, spewing forth unintelligible words in a shrieking gargle of sounds not readily available in nature. Since she can't sing, a sweet young songbird (Debbie Reynolds) is forced to dub the star's voice. But here's the, um, "dub" – though Reynolds was a perfectly perky singer, she ended up with a vocal stand-in of her own. The ballads "Would You" and "You Are My Lucky Star" were ultimately sung by the uncredited Betty Noyes. Cue the wordplay on "Noyes" and "noise" ... heaven knows, the woman should have made some.

Flashing forward to today's movie musical, the tradition has changed – dubbing is no longer acceptable. It's thought to be "uncool," even gauche. Ergo, all of Nine's stars are singing for their own supper. Aside from Daniel Day-Lewis, the actor/singers include Judi Dench (the original Sally Bowles in the 1968 London staging of Cabaret ), Nicole Kidman (Moulin Rouge), Marion Cotillard (La Vie En Rose), pop star Fergie, Kate Hudson and Sophia Loren. Even Penelope Cruz, who admits to only having sung with a Karaoke machine before filming Nine.

Which leads us to a final, delightful refrain: in the celluloid world of breast, buttock and cheek implants, rhinoplasty, assorted face lifts, tucks, and eye jobs ... it's the voice that has to be real.

What a lark.