The 1961 film, directed by Jerome Robbins and Robert Wise, is an updated version of Shakespeare's "Romeo and Juliet." Tony (Richard Beymer), member of the American Jets gang, falls in love with the sister, Maria (Natalie Wood), of the leader of the Puerto Rican Sharks gang.
Various actors' vocals were dubbed for the film, including Beymer's and some of Wood's. Actress Rita Moreno, who played Maria's brother's girlfriend, Anita, sang some of her songs herself but also had sections dubbed by singer Betty Wand. On one particular day, Moreno was unable to record her own vocals as planned because she was ill and Wand was sick, too, so singer Marni Nixon, who was handling some of Wood's vocal parts, sang Moreno's as well.