Good video, thanks! I also found the next vid in line was fun to listen to:The mixing desk 'encoded' nothing.
If you really want to know how it worked, this ex-Decca engineer explains how Phase 4 Stereo was recorded and mixed. Odd that he forgets to mention anything about surround sound! Note that he does say that Decca deliberately chose a microphone technique that minimised any pick up from the rear and thus avoided any of that bloom (or ambience) they were actually desperate to strip out!! -
Decca