Madonna Performs Elliott Smith's 'Between the Bars,' Mingles With Sean Penn at #secretprojectrevolution Film Launch

Madonna and Rocco
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Madonna and Rocco Ritchie perform during Madonna and Steven Klein #secretprojectrevolution at the Gagosian Gallery on September 24, 2013 in New York City.

In a 2006 interview with Q magazine, Madonna was asked which song of the last 20 years she wished she'd written. Her answer: Elliott Smith's "Between the Bars," an aching ballad the late artist contributed to the "Good Will Hunting" soundtrack. On Tuesday night at an event in Manhattan launching the short film, "secretprojectrevolution," part of her Art for Freedom campaign, Madonna sang the song she wishes was hers.

After being dragged on stage by two actors dressed as police officers, one of whom shoved a microphone in her hand, Madonna delivered a delicate and emotional rendering of the beloved song while accompanied only by a piano.

Halfway through the performance, a kneeling Madonna was accompanied by a masked dancer dressed head-to-toe in black who freed one her bound hands. When the song concluded, the dancer took off his balaclava to reveal his identity: none other than Madonna's 13-year-old son, Rocco. Watch:

Madonna's performance of "Between the Bars" comes less than a month before the tenth anniversary of Smith's death. The singer, who scored an Oscar nomination for another "Good Will Hunting" track, "Miss Misery," died Oct. 21, 2003 of stab wounds to his chest 

"This film, aside from my children, is to me the most important thing I've ever done," she said. "The idea of being free, and being able to express myself, not only as an artist but as a human being, is extremely important and I do not take my freedom for granted. And it seems to me, when I travel around the world, that people are either not free and are fighting for it, or are free and  taking it for granted. And both of those situations make me extremely agitated."

"God made art," she continued. "God made human beings to create art. We are channeling God when we make art. I do not doubt that for a minute and it's nobody's business to get in the way of that. Amen."

Tuesday's event was held at the Gagosian Gallery in New York's Chelsea neighborhood and was attended by CNN's Anderson Cooper, blogger Perez Hilton, Lucy Liu, Zachary Quinto, Donna Karan, Lindsay Lohan and Madonna's former husband Sean Penn.

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Sean Penn and Madonna attend Madonna and Steven Klein #secretprojectrevolution at the Gagosian Gallery on September 24, 2013 in New York City.