Most popular albums through roughly the end of 1967, especially in the U.K., were mono mixes. The stereo mixes were an afterthought because stereo systems were still a luxury and not commonplace in most homes. And, of course, there was the AM radio factor. Many UK stereo mixes of that era were horrible things with voices on one side and instruments on the other, very disconcerting to say the least.
U.S. stereo mixes were generally better even when they took a mono mix and tarted it up. The early Beatles albums in the U.S. come most notably to mind. However, beware of any record that says it is "electronically reprocessed for stereo."
So for every Beatles record up through and including Pepper and other classics like the first Buffalo Springfield album, the mono mix is the one the band was associated with and signed off on. The stereo version was thrown together in an afternoon. Check Mark Lewisohn's "The Beatles Recording Sessions," and you'll see that was the case. I also highly recommend Geoff Emerick's book, "Here, There and Everywhere," to get the chief recording engineer's perspective on the Beatles' sessions: It's the first new Beatles book in years that is worth reading - from the only person other than the lads themselves and George Martin who was actually in the room. Not counting Neil and Mal, of course, who weren't part of the recording process.
Those mono mixes are much richer and feature much more sophisticated instrument placement than many people realize. That said, there were some excellent stereo recordings coming out in the period, especially from the majors like Columbia and RCA. The Byrds and Airplane LPs sound great in stereo to this listener. But the first Spencer Davis album sounds much better in mono. Same goes for the early Animals and Hollies records. The Beach Boys albums through the end of the '60s should only be listened to in mono, although they've done good work on them in recent years. Even a record like the Buckinghams' first for Columbia with Don't You Care and Mercy Mercy Mercy is a joyful surprise in mono.
Anyway, yes, there are some major differences between the Beatles stereo and mono mixes. Ringo doesn't bark, "I got blisters on my fingers" on the mono mix, for example. The mono Pepper sounds noticeably different on several songs in terms of background vocals, extended laughter on Within You Without You, extra drum pattern in the Reprise, stuff a Beatles nut would notice because he/she knows the songs so well. But, that said, the stereo mixes IN THE U.S. were quite well done and are the ones most of us have known for 40 or more years.
So are the mono mixes worth buying? I have most of the early Beatles albums in mono already because I just had a cheap little non-stereo player at that early age, but, of course, I've picked up the stereo versions since then, both US and UK. But for me the mono mixes represent the records that the Beatles worked on themselves for release: That's the way they heard them in final fashion when they walked out of the studio. They're the first editions, if you will, as released to the British public. So I want them for that reason, if no other. I'm sure the forthcoming stereo remasters a la the Love CD will be spectacular, and I'm sure I'll ultimately buy them. But for now, closet Luddite that I am, I want to hear the Beatles in glorious EMI / Abbey Road mono.
