Actually, everything that the BRILLIANT Eddie Kramer did you will find is phase correlated, and "dimensional".
If you listen through good, phase accurate headphones (i.e. in stereo) you will hear this, alternately you can get creative and hook up speakers USING A STEREO AMP (i.e. NOT a "surround receiver") with the speakers matrix-connected, you will EASILY hear how on some songs the guitar is ONLY behind you, etc. Every song on Electric Ladyland has a slightly different trick, from backwards tape to phased panning to "real" reel-to-reel phasing (my fave) to capstan motors starting up on echo tape delay machines, to capstan motors speeding up as the return is panned...(die, die, die...) and so on.
And to think all this was done in '68.
I posted a quick sketch of how to connect the speakers here:
You can also take any old car radio with a "fader" control, lift the grounds on the 2 back speakers, and now you have a HUGE acoustic space in the car!
You can LEAVE your regular 2-channel setup the way it is, find another amp, and take a feed from the L HOT and R HOT terminals THROUGH A PAIR OF 1K BUILDOUT RESISTORS, (with a 3rd, 1k terminating resistor) and feed THAT into another, totally separate amp, which "normally" feeds another pair of speakers that you now place behind you.
Sorry that the whole matrix surround business has fallen so far off the wayside and off everyone's radar. ANY stereo system can be VERY enhanced with the careful and appropriate addition of these differential phase reproducing surround speakers.
On many recordings, what you will hear is the "echo" (more accurately called reverb) part of the signal, since it is typically the only thing in the stereo pair that has mostly out-of-phase correlation.
In case any of you young-uns don't know what this is, it was originally called Hafler Dynaquad, and formed the basis for ALL the quad "retrieval" systems of the 70's, from QS to SQ to Sansui, etc et etc. All of these systems extracted sum and difference information from the stereo channels, in a pretty simple mathematical way, using opamps.
There si no messy digital processing involved (nor should there be). ALL the "3D" information is present in the stereo image, although some magazine writers have suggested that the information is "folded down", because when recording with a pair of spaced omnis, it is not necessarily possible to determine if an instrument is in front of you or behind you, since there is no APPARENT phase differentiation between front and back as you move the source instrument...
So each part of this discussion opens up a whole new can o worms. What about head transfer function? What about actual surround recording mics? What abou all those cutesy "surround" plug-ins that these ProTools guys use, which include circular panning, and psychoacoustic imaging? How do people with "stereo" reverb systems make it work in surround?
How many discrete channels are there REALLY?
There are PLENTY more panning and phase -related tricks that Eddie Kramer pioneered - also examine Led Zep II... remember the pre-groove echo trick?
And last but hardly least, examine the mix of Madonna's VOGUE, which was mixed with Q-sound, circa 1992.
Hey, enjoy. Lift those speaker grounds and experiment away...