STRADIVARI'S SECRETAttuned to chemistry of a genius Some doubt his technique, but scientist says he's found key to legendary soundA starter violin costs about $200. A finely crafted modern instrument can run as much as $20,000. But even that's loose change when compared with a violin made three centuries ago by Antonio Stradivari. His 600 or so surviving violins can cost upward of $3.5 million. For more than a century, artists, craftsmen and scientists have sought the secret to the prized instruments' distinct sound. Dozens have claimed to have solved the mystery, but none has been proved right. Now, a...