From the Musical, West Side Story, by Leonard Bernstein and Arthur Laurents

A heartbreaking revision of Romeo and Juliet conceived and directed by Broadway mainstay Jerome Robbins, this boundary-breaking interracial love story starring Natalie Wood as the Puerto Rican Maria and Richard Beymer as the lily-white Tony, is what all big-screen romances aspire to be. The dance sequences are amazing and the songs are eternal, but it's the passion that keeps fans coming back decade after decade.

Tony and Maria sing this beautiful song after taking their wedding vows, knowing they are not likely to survive the night.  I find the accompaniment especially lovely.