Jim Carroll wrote:

"Any interpretation of a song has to start and end with the text (the tunes are invariably a moveable feast)."

I disagree. A song is about words AND music. Both are equally important. It is the interrelationship between the two that makes the song. The nature of the melody, major or minor - which can set mood, how the words interact with the shape of the melody, the relationship between the phrasing in the text and the musical phrases and the tempo all affect how you might interpret a song.