It's a classic, and probably everyone's heard it already. But I never really got into sort of folky-type music.
It's Tim Buckley's 'Song to the Siren'.
How this passed me by for all my 34 years I really don't have a clue. It's total genius. Go to the iTunes music store and buy it, and if you don't like it I'll send you your 79p / 99c by PayPal.
Man. Talk about utterly, devastatingly heartbreaking.