Once upon a time in the mid 70's I had an Electro-Voice 7445 encoder. Everybody loves big VU meters but except for that it was a pretty ugly box. Knock your knuckles on it & it sounded empty like the Tin Man. Open it up & it had very little circuitry, no IC's just discrete transistors. But that was part of the beauty of EV 4: just a bit of in phase blending of the encoded front chs, and quite a bit of opposite phase blending on the rear encoded chs. QS or SQ by comparison required much more.
Of all the non-separation enhanced decoders I think the EV system was the best. In stereo or encoded it gave what people expected: reasonably wide front left/right separation and good depth in the rear. I bet store salesman back then could play some Enoch Light & Eknock the socks off a listener hearing quad for the first time.
To bad they dropped that scheme & screwed up by releasing the EVX 44.
I loved my two Encoders RM , and SQ , and they are a lot of fun when your encoding in matrix quad,... discreet albums such as CD-4 .
I have on SQ cassette The Doobies Brothers, Eagles One Of These Nights ,
Frank Zappa , Passport, Harry Nilsson, Jefferson Airplane, The Outlaws, Creedence Gold , ...and a few other gems.
Q8 for me was a bit more problematic , what with all that tape hiss present.
Nevertheless I did encode some Capitol albums to SQ , like both Steve Miller,
some Grand Funk , Paul McCartney, and John Lennon Walls And Bridges , and one or 2 Steely Dan , and Joe Walsh albums, amongst a few others.
That EV-4 Electro Voice , would probably be loads of fun trying out EV-4 in comparison to other albums you had in Discreet . And perhaps some that were SQ and QS , that you had of discreet versions .