QuoteFor years, stations have paid royalties to composers and publishers when they played their songs. But they enjoy a federal exemption when paying the performers and record labels because, they argue, the airplay sells music. Now, the Recording Industry Assn. of America and several artists' groups are getting ready to push Congress to repeal the exemption, a move that could generate hundreds of millions of dollars annually in new royalties. Mary Wilson, who with Diana Ross and Florence Ballard formed the original Supremes, said the exemption was unfair and forced older musicians to continue touring to pay their bills.