

LPs were going stereo. Western Electric had pioneered the Westrex process called 45/45, a single groove stereophonic system. The important part is that existing monophonic equipment could still play the Lps ensuring instant consumer acceptance. It worked. Western Electric was the manufacturing arm of AT&T for the better part of a century. They started out in the 1850s making typewriters.
In the 1970s, the now flat-sounding mono records were commonly rereleased with "enhanced" sound. this was also called "Duophonic" sound after the Capitol records process. These were marketed as stereo versions of the original releases. But the monophonic master tapes had no stereo separation. So they had to fake it. The stereo effect was created through a couple remarkably simple techniques. Some audio filtering was used to separate out certain sounds to pan them. This usually produced noticeable audio artifacts. Also common were slight adjustments in EQ and phase which is what RCa seemed to focus on. An offset of 20 and 50 milliseconds was another very rudimentary change that mimicked the stereo effect.

