The classical music world has always liked to consider itself above such plebeian niceties as marketing or salesmanship. Still, artists like Lara St. John, who appeared on her first album cover wearing nothing but a violin held across her bare chest, force everyone to confront the fact that sex and physical beauty sell albums, whether you’re hawking Bach or rock. But for St. John, her lithe and alluring frame has been a double-edged sword. Yes, it got her noticed, but classical snobs have a habit of dumping everything that looks pretty into the much-derided “crossover” bin, and for St. John, a serious artist who plays serious music, that creates a distressing image gap.