It started as a hum that filled the silence of the car when there was nothing on the radio and Sam had had enough of the greatest hits of mullet rock. Dean of course hadn't minded at first, as long as Sam was humming he wasn't attempting to make awkward highway conversation.
As the night grew darker however, Dean began to make out some of the words Sam was attempting to sing as he became louder and more off key as the song progressed. Dean soon realised the song on Sam's IPod sounded strangely familiar but he couldn't place what it was or where he had heard it before.