Susan Sarandon would be the first to admit that she is not exactly in the Julie Andrews league when it comes to belting out a show tune.

However, she has found herself called to break into song in a surprising number of movies, right from the days when, as the virginal Janet in The Rocky Horror Show, she pleaded " I wanna be dirrrty".

She is at it again as in Romance and Cigarettes as Kitty, the cuckolded wife of James Gandolfini. After discovering his infidelity she finds herself in church giving a rousing rendition of Janis Joplin's Little Piece of My Heart with a choir led by Eddie Izzard.

"I've been singing badly in movies constantly," she says. "I sang in Dead Man Walking, in Anywhere But Here, in The Banger Sisters. I'm always singing a little ditty here and there.

"This was different. The people in this film when they get to a certain point where they need an emotional vocabulary, they chose a song to vocalise those emotions.

"Until I did that scene I'd never heard the words the way that I did that day. I never really understood that what she was saying was 'I've given you everything and what do you do to me? You've f****d me over - well why don't you go ahead and take the rest of my life. Just take it. I dare you'.

"I never understood it, just the way my kids sing these horrible songs about drug addiction and suicide and I think 'do you know what you are talking about?'."

She credits her three children - daughter Eve from her relationship with actor Franco Amurri, and Jack Henry and Miles Guthrie, her sons with partner Tim Robbins - with keeping her "up to speed with everything from The Killers or Keane".

"In our house we go from The Clash all the way through to the other end of the spectrum. I think some of my boys have hearing loss, including Tim, everything's so loud."

She has reciprocated by introducing them to some classic "oldies" that date as far back as the 80s.

"I introduced them to Prince the other day. I had tickets to see him and then got stuck in Texas. They went and when I came back and they were like 'Mom you won't believe it - he's such a good musician!' I was like 'Yeah. Duh!'.

"Eddie Vedder's a really good friend of ours, so a lot of of their first concerts were things like Pearl Jam and Springsteen."

Romance and Cigarettes is a working class soap/opera, the story of blue collar family torn apart when the portly patriarch Nick (Gandolfini) has an affair with a flame-haired, foul-mouthed temptress played by Kate Winslet.

Understandably enraged, wife Kitty throws him out of the marital bed only to relent when fate throws them an unexpected - and terminal - curveball.

To Susan it is the idea of emotional rather then physical infidelity being more important to Kitty that intrigued her.

"My feelings about infidelity have changed as I have gotten older and made more mistakes myself and I have been tempted more myself.

"I don't think it is the physical affair that upsets her (Kitty), for me it is the fact that he wrote a poem.

"It is the idea of being madly in love and cherishing someone and missing that in your marriage and seeing your partner in that intoxicated state of falling in love that is so hurtful.

"I don't know that people are meant to stay together for years and years without making a mistake. I think it is very difficult to be married and to be monogamous, but what would really kill me is that he wrote the poem, even if it is not a very good poem. It was stepping over the line.

"Everyone has to figure out what that line is. What you find personally compromising. You can only be humiliated if you allow yourself to be humiliated."

The image the actress gives to the world is that she is nobody's victim. Her heritage is a fiery combination of Italian (on her mother's side) and Welsh (on her father's).

The union between Susan and Tim, who at 47 is 14 years her junior, is viewed to be one of the strongest in showbusiness.

She once quipped "Tim and I just celebrated 17 years together, which in Hollywood years is 45 I think".

They are both political animals, involved in left wing and liberal causes, and while co-presenting at the 1993 Oscars they famously went off script to draw attention to the plight of Haitians with Aids who had been interned in Guantanamo Bay.

These days they are not alone in their outspokenness about issues that concern them.

Actors such as George Clooney for instance have been equally vocal when it comes to questioning the Government's actions in Iraq. However, Susan admits that sticking to their convictions has come at a high price. They received death threats, their phone was tapped, they were attacked in the press and, she reveals, there were failed attempts to get actors like them and Clooney blacklisted.

"It is not as bad know as it was before the war. In the lead up to Iraq you could have heard a pin drop. That was so scary. I was getting phone calls saying 'be careful'.

"OK so now we know there weren't weapons of mass destruction, now we know we were lied too. But in the beginning, when I was just asking 'can't we slow down, Let's leave the weapons inspectors in. Why are we going to war?' there were papers that called me a 'Bin Laden lover'.

"I had a lot of talk show hosts telling people to hurt me. It made me upset and angry. But supposing I hadn't questioned going to war and there were hundreds and thousands of deaths and people losing arms and legs.

"I don't feel vindicated but I certainly would have felt horrible if I hadn't said something.

"You don't worry about whether you are going to lose work over it. That's like fleeing a burning building and wondering whether your slip is showing. You have to do what you have to do and, at the end of the day, I have no regrets."

* Romance and Cigarettes is currently on general release. ..SUPL: