One of my earliest memories of being moved by the atmosphere of a song was Simon & Garfunkel's The Boxer. I was totally unprepared for the way the song expanded beyond the simple guitar and harmonies. I just remember the sheer exhiliration I felt as the song seemed to swallow me whole with its sound and emotional crescendo, the melodic motif repeating itself and growing increasingly larger and all encompassing. I remember thinking that everyone in the world must be hearing what I was hearing at that moment so engulfing was the song's atmosphere. And then it ends.

I didn't know it at the time but when the song ended after that first hearing it was destined to be one those songs that, in truth, would never end such was its instant mark of indelibility, it would always be playing in my life even when I wasn't listening to it.

Conjures up the atmosphere of floating down a stream on a sunny day

You could cut it with a knife. Sigur Ros singing Vaka on the Heima DVD is one of the most atmospheric things you could come across.

Great track, but the wassock who created the clip before uploading it to Youtube used a photo of Blind Wille McTell instead of one of Blind Willie Johnson.

Incidentally, Dark Was The Night is one of the tracks on The Golden Record, copies of which were attached to the two Voyager probes which were launched in 1977. The Golden Record includes extracts of speech in over 50 languages, various sounds from earth (both natural and man-made) and 90 minutes of music. As well as Blind Willie Johnson, the music portion includes works from JS. Bach (three selections), Beethoven (two selections, including the first movement of the Fifth Symphony), Mozart("Queen of the Night aria from The Magic Flute"), Stravinsky, Louis Armstrong and Chuck Berry ("Johnny B. Goode").

If an alien race ever does discover these problems, many millions of years into the future, mankind will probably be long gone - yet Blind Willie Johnson will live on.

but still the best.

has many, many songs that would fit in here, but I'll go with these two.
'Hello Earth' from The Hounds of Love. The whole of the second side is bursting with atmosphere and any track would do, but I love this one because of the male voices (according to Wikipedia - The chorale in "Hello Earth" is a segment from the traditional Georgian song "Tsintskaro," performed by the Richard Hickox Singers).
It's an extraordinary and beautiful song.

And this, 'All The Love' from The Dreaming. I used to play this album every week when travelling home on the train (cassette - walkman!) and this sounds amazing on headphones.

One more!
Japan 'Taking Islands In Africa' from Gentlemen Take Polaroids.
Another very atmospheric band and this is fantastic on headphones (and almost as good without).
Probably my favourite song of theirs, too.

was the inspiration for this. A tribute,A homage if you will