Today on Felthry Overthinks Things: Headphones in a world where people have all sorts of different body layouts and might have ears in weird places.
I would guess that--for ideal surround-sound experience--there'd have to be software stuff for marking where each ear is, and then the music files would be encoded as multiple parts with 3d locations for each source, to determine phasing and other inter-aural characteristics.
@Felthry No, but it makes for a damn good marketing ploy. :B