The distinction that one is a pre-sale freebie used to encourage sales and the other is a value-add on items sold seems critical to me. I’m going to shamelessly swipe that idea from now on. :)
It seems to me that that this also gets to the issue of how you’re monetizing music. If you’re aiming to make money on upsales to merch and tickets, use a song page. If you’re aiming to make money on downloads, use a… Dunno what you’d call it, but it’s a different flavor of this concept, anyway.
I can also imagine a hybrid business model where you’re selling plain ol’ downloads, but authorized downloads have a way-cool page in the link and downloads from filesharing networks have a skanky sleazeware site in the link.