I can't find where in Billboard I read that The Welk Corp acquired all of Project 3 Records on Paramount ,later to become ABC/Paramount ,
Enoch Light was retained as Project 3's Director.
So I'm not certain what year they stopped with quad recording ,but if I had to guess I'd say late 75 or early 76.
Enoch Light , passed away in 1978 at age 71.(BB Aug 12 78 pg 06).
Sad of course, But what an amazing Quadraphonic Legacy he has left . And we're still discussing his quad recordings even today in the new millennial.
ABC/Paramount acquired Command Records, which was Light's label before Project 3, in 1959. They actually wanted the assets (masters etc.) of the label he'd started even before that, called Grand Award, which is why the deal was done.
Little did they know that Light had just finished recording the
Persuasive Percussion album while the deal was being done, and shortly after it became a massive sensation - it was the first blockbuster stereo album, and ended up spending nearly 3 months at #1 in the Billboard chart and sold well over a million copies, making Light a star in the early '60s in the process.
The funny thing about it was that ABC-Paramount didn't want to release
Persuasive Percussion at all - Light had to do a lot of arm twisting to get it released, and the reason that it was released on Command and not Grand Award is that Light created Command especially for the album so that if (or when) it failed, it wouldn't tarnish Grand Award's reputation. In fact, the opposite happened - Persuasive Percussion was so popular that Command became Light's premier label and he stopped putting out anything new on Grand Award shortly thereafter.
Light stayed as director (I think his official title was vice-president) of Command under ABC-Paramount until late 1965 or early 1966, and released a ton of very successful albums, under his own name, as well as producing a number of artists including Doc Severinsen and Dick Hyman, and all of the various "Command All-Stars" albums, of which
Persuasive Percussion was the first. Command is also arguably the first "audiophile" label - they listed the equipment used on the album sleeves, and they made a big (huge) deal of the fact that their albums were recorded on 35mm film, which produced a superior sound quality in the days before 1" and 2" tape technology was really perfected. It's no wonder either, as all of Light's Command albums (and the early Project 3 albums) were engineered by C. Robert Fine, famous for his Mercury Living Presence classical recordings in the 1950s.
As I mentioned, Light left Command toward the end of 1965 because he wanted to start his own label - one he controlled and owned, and that's when he started Project 3. The name itself is a reference to the fact that the label itself was the third one he'd established. RCA courted him heavily - they wanted him to set up a label called RCA Enoch Light - but they wouldn't give him full control or ownership of his masters, so he ended up going into partnership with the Singer Corporation (yes, the sewing machine people) and started Project 3. Within a year or two he bought Singer out and gained complete control of the label making it truly independent.
Light's reputation as a sonic innovator and audiophile (not to mention Project 3 being one of the first labels to release quad material) was such that when ABC started releasing quad LPs in 1971, the reactivated Light's old Command label to do it, calling the series Command Quadraphonic and releasing a half-dozen old Command albums, including Doc Severinsen's
Fever, Persuasive Percussion, and Light's
A New Concept of Cole Porter Songs even though Light had been gone from the label for 5 years by that point.
Despite what it says on Wikipedia, Light didn't "retire from the industry completely in 1974" - he remained in charge of Project 3 right up until his death in 1978 and they continued releasing quad albums (albeit at a slower rate after about 1975) up until 1977.