One (also known as One (Singular Sensation)) is a song from the musical A Chorus Line.
Director Michael Bennett explained his view regarding the song's inception and placement within the show:
I want the audience to walk out of the theatre saying, 'Those kids shouldn't be in a chorus!' And I want people in the audience to go to other shows and think about what's really gone into making that chorus . . . It fades with them kicking. That's it. That's the end of the show. There are no bows. I don't believe in bows, just the fade out. That's what a dancer's life is.
The dancers finally dance the chorus number for an unnamed and unseen star. They are all wearing uniforms so it is impossible to tell them apart. The uniqueness that made them all so interesting throughout the show has now been damaged by the reality of show business.
Musicals101 explains the song.
CityBeat described it as "the show’s greatest emotional wallop". The Davis Enterprise dubbed it the show's " signature tune".