Madonna debuted a new song, backed by her son Rocco, in New York City last night (24.09.13).

The 'Music' singer launched her #ArtForFreedom project with a huge party, at which she debuted the new mystery track and filmed the #SecretProjectRevolution film, directed by Steven Klein.

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