The operation, called Huge Music, will be led by the former EMI promotions and licensing manager Fiona McBlane.
She will work with a group of WCRS staff to build relationships between the music, film, television and advertising industries.
The division will cover all aspects of music licensing, from music research and clearance for ad agencies to music supervision on films and TV series.
The operation aims to service non-WCRS clients and will be approaching other ad agencies as well as TV and film production companies.
McBlane will report directly to the WCRS chief executive, Debbie Klein.
Klein said: "As the boundaries between music, advertising, TV and film become ever more blurred, Huge Music is ideally placed to create new opportunities for our clients and their brands."
The new division's first project has been to source the music for WCRS's new Bulldog Communications ad. It is already working on various other projects for the agency.
McBlane has worked at EMI for the past eight years. She was responsible for licensing tracks including The Prodigy's You'll Be Under My Wheels for WCRS's BMW spot and Robbie Williams' Millennium for Rainey Kelly Campbell Roalfe\Y&R's Lloyds TSB work.
McBlane said: "I'm thrilled to be given the opportunity to bring my contacts and knowledge of the music industry to the world of advertising."
The new division is part of a WCRS strategy to develop non-traditional advertising revenue streams. Its group company, recently rebranded as Engine, has set up a range of agencies, including the direct marketing agency Personal, the branding agency Dave and the sales promotion agency Woo.