"Loverly" soprano Marni Nixon has ensured herself a proper place in film history although most moviegoers would not recognize her if they passed her on the street. But if you heard her, that might be a horse of a different color. Marni is one of those unsung heroes (or should I say "much sung" heroes) whose incredible talents were given short shrift at the time. For those who think film superstars such as Deborah Kerr, Natalie Wood, and Audrey Hepburn possessed not only powerhouse dramatic talen...