Showing The Case of the Lost Song by Carolyn Keene

AT A TRAVELING ANTIQUES SHOW, NANCY'S APPRAISING BURGLARIES, FRAUD, AND A GREEDY THIEF!
While visiting Chicago, Nancy, Bess, and George bring some items to the Old Can Be Gold show to see what they're worth, just for fun. In George's old tape recorder, a dealer finds a rare early tape by a famous rock group. But before George can get it insured, it's stolen -- like many other items brought to the show!
From a luxury condo on Lake Shore Drive to a hot blues club, Nancy discovers a mix of suspects. There's a seedy dealer, an ambitious publicist with access to the show's database, a talented singer in need of money, and drop-dead gorgeous twin brothers, one a top appraiser and the other a gifted photographer. Nancy's got to wind up the case -- before a desperate con artist erases her for good!