(NME.com) -- BONO joined THE ROLLING STONES onstage in CHICAGO last night (September 16) to work through a version of the band's 'IT'S ONLY ROCK AND ROLL'.

The U2 frontman strolled on unannounced halfway through the The Stones' set at the 5,000 capacity Aragon Ballroom. He said nothing, but simply sang the song, and wandered off at the end.

Bono is in Chicago ahead of an appearance on the Oprah Winfrey show today (September 17). He will talk to the chat show queen about his campaigning for people in developing countries. The show will be broadcast in the US on Friday (September 20).