The original
Elton John recording of this song is a person trying to express his feelings for someone, but he is very
nervous and
uncertain, afraid she will stop listening at any time. It is a beautiful, quiet love song. The
Moulin Rouge version is different.
It is sung by Ewan McGregor as Christian as his audition to Satine, so he can write her play. The problem is that she thinks he is Duke, a potential investor for the play, whom she has to woo so he will agree to give them the money. He begins just speaking the first verse, and she isn't really listening; she's rolling around, acting like his words are turning her on.
Then he breaks into song on the line, "my gift is my song," and she is stunned into silence. It is much like an earlier scene, in which he was trying to suggest a line to the Bohemians, but they were all arguing over it and didn't hear him until he sang.
The rest of the song, he sings to Satine, and she is spellbound. There is no more of the diffidence of the original song; instead, it is a poet, doing what he does best, growing more confident with every line. He has already fallen for her while watching her perform in the club, and now she falls for him.
When she discovers that he isn't Duke, and in fact the real Duke is just coming in the door, she makes him hide, and she uses the song to keep Duke distracted so Christian can leave. Unfortunately he can't, so she gets Duke to leave instead. She tries to pretend she doesn't really love Christian, but she does, and that is the central point of the movie.