Here are excerpts from the Sonic Seasonings 2 CD re-issue from East Side Digital in 1998:
"There is a long-overdue demand for a definitive two track stereo re-release of Sonic Seasonings. New developments will make it possible to do a real multi-channel stereo version as well. That will be personally very satisfying to me. After all, back in 1971, I had requested that CBS release the album using the then new CD-4 true Quadraphonic system. CBS refused, wishing to use their imitation, psuedo-quad compromise, SQ. A standoff.
Another big surprise after all these years is that two track stereo is still the standard, most popular method of music reproduction found in the world, a status not about to be replaced anytime soon. This deluxe edition will therefore satisfy that genuine need.
We have used every possible care to insure the integrity of this digital master to the original mixed tapes. The actual 3M tape machine used to record those first generation surround masters was painstakenly refurbished and brought up to spec. Other than Dolby, no auxiliary equipment was placed in the circuit path into our high resolution A/D convertors. The 4 to 2 channel "fold-in" reduction was fed directly to the DAW, replicating the process I'd developed originally for our CBS two track masters, including that "nearly quad" property. I hope you enjoy hearing all the details, clarity and sonic details, clarity and sonic depth that remained inaudible until now."
- Wendy Carlos, 1998
In summary: Her process must be quite complimentary to matrix quad techniques. It sounded discrete to me, but then, without having ever heard the quad version, I've no way to know what she intended. All I know is that it's wonderful and proves she was way ahead of time, as other works surfaced years later by others like Brian Eno.
I'll be glad when the real mccoy DVD-A/SACD is issued and we'll chuckle about these discussions!
timbre4