So what's the tech angle? Will.i.am is Intel's Director of Creative Innovation. You may remember him from such things as the Ultrabook Project:
The member of the Black Eyed Peas will be participating in an arts project facilitated by Sydney-based arts company, Spinifex, which will be an interactive lighting display on the facade of the recently-renovated Museum of Contemporary Art. A purpose-built interface will allow the public to "play the building", using projections from Sydney artist Justine Williams and will.i.am's music.
This interactive display will be part of the Vivid Sydney event, which will run from 25 May until 11 June.