I remember when this came about. It was explained to me that microphones and instruments were not always in phase with each other and therefore the effect varies from recording to recording. As a good example is The Lovin’ Spoonfuls ‘ ‘You didn’t have to be so nice’ ...
Those early LS records (plus many other 'groups' back then) were a recording patchwork. Probably because studio time was expensive, and because the actual band members were often inexperienced. Record labels employed union hourly rate studio musicians who laid down the basic tracks, then singers added their contribution, with the final mix assembled almost willy nilly. You can tell that little thought went into it. Especially since the pop stuff was 'meant' for AM car radio, the source being a 45rpm played with something like a Stanton 500, talked over by a DJ. Actual production 'values' secondary to the money-making endeavor.
As I recall, Spoonful stereo records typically had vocals on on channel, with instruments on the other. Sometimes there was little in between.
I hadn't listened to that particular track in years, but just did. A very simple mix. Basic instrumental track recorded in monophonic, more or less smack dab in the middle of the mix. Sebastian's voice is on the left channel, background chorus on the right. John's voice does have an 'out of phase' character to it.
Alternately, you often had some pretty intricate and well thought out productions, featuring multiple musicians, mixed into mono-- the idea that what you heard would not so much be different instruments playing different parts, but something fused into a single 'studio' instrument, as it were. Phil Spector and Brian Wilson come to mind. Compare the intended mono mix of
Be My Baby with some subsequent 'stereo' reissues. Even in mono, the driving beat of Hal Blaine's drum carried the recording, and you can hear the studio's natural reverb in his drum (and in the other instruments-- I'm assuming that there was no added reverberation, but I don't know that).
I mean, the Wall of Sound technique is sometimes considered 'unnatural', but in spite of their depth, those recordings have a naturalness you often don't find in a lot of subsequent, more electronic processed productions. For his part, Wilson claimed he always liked to use Gold Star (along with Western) because of the studio's reverberant acoustic.
Somewhere around here I have the
Pet Sounds box set, that features two CDs highlighting the evolution of Brian's final product, as the Wrecking Crew goes through multiple takes. Unlike a lot of today's pop, you had acoustic instruments (horns, harmonica, upright bass, banjo, piano etc.) playing along with six and twelve string electric guitar, organ and electric bass, --and interestingly enough, in the stereo mix you can hear each instrument clearly in an ambient stereo. Most of that was lost in the final product that Brian mixed down to mono.
Now I see that there is new a 5.1 mix of the record. I don't have a surround system, so I have no idea how it compares with either the subsequent stereo mix, or original monophonic.