QUADRAPHONIC RECORDS

It works similarly to how stereo radio works on a mono transmitter - the rear channels are on the "upper-deck" between 20kHz and 40kHz, and have to be decoded by a special phono preamp, provided the cartridge can do the frequency range required. They used to make cartridges capable of this at the time Quadraphonic was popular, but you see, CD took over around that time, and all was lost....

Bruce, you are missing none of the musicality because of your equipment, but you most likely are missing some because of the way the record is engineered. You appear right from the limited information and memories I have regarding "frequency stacking" and it should now appear obvious that to ensure the "stacked" rear signals are not corrupted (too much...) by modulation, the stereo upper frequency limit is filtered more aggressively than it would on a stereo-only record.

There has been quadraphonic "technology" and there has been "quadrasound". I am sure there was not only one standard for cutting and reproduction of quad because it seems, nobody on this planet can agree, and because there was no big money to be made out of quadraphony no single standard would have emerged (usually through the courtrooms...)

I have just one quadraphonic pressing: Joe Walsh "The Smoker You Drink The Player You Get", and I also own a stereo version. The term to describe the quadraphonic version is I think "darker", or I would loosely call it in casual conversation, not as "juicy", probably because of the aggressive top-end cut.