Madonna debuted a new song, backed by her son Rocco, in New York City on Tuesday night.

Madonna's new ballad started off with her on her knees at the front of the stage, accompanied by just a piano. After three minutes she was joined by a mystery dancer - dressed head to toe in black and clad in a balaclava - who turned out to be Rocco, 13, who did an interpretive break dance to the song.

Stars gathered at the event included Madonna's ex-husband Sean Penn, Lindsay Lohan, Anderson Cooper, Donna Karan, Zachary Quinto, Calvin Klein and David Blaine.

The '#SecretProjectRevolution' film was also broadcast at venues in other cities around the world, including Los Angeles, Berlin, London and Toronto.

In the movie Madonna can be seen dressed as a prisoner/jailer while the content includes a lot of artistic musing over concepts of democracy.

A post on the project's website states: "Madonna & Steven Klein invite you to start your own revolution of love. We have created this platform to give people around the world an opportunity to answer the question:

'what does freedom mean to you?' "

For more information and to see the film, visit artforfreedom.com