But also gathering heat are protests over its controversial content, with a United States anti-porn group launching an attack over the rating awarded by the Motion Picture Association of America.

The film, based on EL James's bestselling 2011 erotic novel featuring themes of bondage and sado-masochism, has scored a R rating, not the maximum NC-17, banning anyone under the age of 17.

Morality in Media (MIM) has slammed the rating, saying the MPAA's description of the movie's "unusual behaviour" does not accurately reflect what the film is about, reports E! News.

"Such a vague evaluation puts viewers at risk, sending the message that humiliation is pleasurable and that torture should be sexually gratifying," it said in a statement.

MIM accused the film of having themes of "humiliation, manipulation, abuse and degradation of women".

It added: "We'd like the MPAA rating for Fifty Shades of Grey to read: 'Promotes torture as sexually gratifying, graphic nudity, encourages stalking and abuse of power, promotes female inequality, glamourises and legitimises violence against women.'"

A literary phenomenon selling more than 100 million copies, Fifty Shades is directed by Sam Taylor-Johnson and stars Dakota Johnson as student Anastasia Steele who becomes embroiled with entrepreneur Christian Grey, played by Jamie Dornan.

Meanwhile, fans are getting teased by music from the movie's soundtrack.Two songs have been selling well in the US already, and the rest of the album's track list has just been announced.

The two songs that have generated buzz are Ellie Goulding's Love Me Like You Do, unveiled last week and approaching sales of 80,000 on iTunes, and The Weeknd's Earned It (Fifty Shades Of Grey), which has sold more than 100,000 since its premiere in late December, according to Nielsen Soundscan.

Other tracks on the full soundtrack (on sale February 10) include original contributions from Jessie Ware, Skylar Grey and Sia, as well as two Beyonce remixes, including Crazy in Love, and a new version of Annie Lennox's cover of I Put a Spell on You.

Mike Knobloch, president of film music and publishing for Universal Pictures, said that some artists were unfamiliar with or wary of Fifty Shades when approached, "but as we brought them into the cutting room and they saw sequences and talked to Sam Taylor-Johnson, they learned more about the aesthetic and the story – that it wasn't just a kinky, sexy thing, that it was really this romance between a young girl and a broken guy."

But, Knobloch points out that "the majority of commercial artists" featured on the soundtrack "were on board" from the start. "It's known that this a big event."

Here is the full listing:

I Put a Spell on You (Fifty Shades of Grey) – Annie Lennox

Undiscovered – Laura Welsh

Earned It (Fifty Shades of Grey) – The Weeknd

Meet Me in the Middle – Jessie Ware

Love Me Like You Do – Ellie Goulding

Haunted (Michael Diamond Remix) – Beyonce

Salted Wound – Sia

Beast of Burden – The Rolling Stones

I'm on Fire – AWOLNATION

Crazy in Love (2014 Remix) – Beyonce

Witchcraft -- Frank Sinatra

One Last Thing – Vaults

Where You Belong – The Weeknd

I Know You – Skylar Grey

Ana and Christian – Danny Elfman

Did That Hurt? – Danny Elfman

- with USA Today

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