I know there are stereo systems with a "front/back" left and right. My question is can you control "front/back" this with panning when mixing a song? Or is a 4 channel stereo system just sort of faking the 4 different outputs.
There are no stereo systems with Front/Back L&R, they're surround sound systems.
If you want to mix your tune in surround, yes you can control the individual outputs by adjusting the volume in order to pan.
in a way you can play with 3 dimensions:
up-down (frequency, lower freqs sound lower down, think of a riser/builder going up in pitch)
left-right (panning obviously)
front-back (volume, things further away sound quieter)
...of course they only work when in relation to other parts of the track - so you'll need some stuff that you can contrast them to for the listener to get the impression
good examples of an artist who has taken advantage of this (in fact pretty much just made music based on exploiting these ideas) are The Orb, if interested check out their album, The Orb's Adventures Beyond The Ultraworld. its also a fucking good album (trip to it)
Actually theoretically you can make the sound fit surround systems _somewhat_ without making it muddy in a normal stereo mix.
Anyone know if there is a common method for the volume db adjustment amongst all surround stereos when sending to front/back?
(As in that it's the same volume as the sounds that would be sent to the left/right +-x db)