From pitchforkmedia.com:
Why mono? Two reasons. First, pop music in stereo was still a novelty through most of the 60s. Radio was dominated by single-channel AM, and the young people who bought LPs were far more likely to have a mono record player as a sound source. Given their audience and the technology of the time, for much of the Beatles' run, the band themselves considered the mono mix as the "real" version of the record and devoted more of their attention to it. Mono mixes were prepared first with the involvement of the band, and in some cases, George Martin and EMI engineers completed stereo remixes of the albums later, after the group had left the studio. So mono, first off, presumably hews closer to the intentions of the Beatles themselves. It's what the Beatles had in mind, their vision of the records.
Secondly, since the mono and stereo mixing sessions happened at different times, there are differences between the two versions, not just in the balance of the sound but also in the actual content. Different takes were sometimes used for punching in overdubs, or an alternate vocal take might make its way into the mix. Sometimes tracks were edited differently, and would be shorter or longer, and in some cases the tape ran at a slightly different speed, changing the pitch slightly. Some of the differences are subtle, and some are not. The mono version of "Helter Skelter", to take one example, is a minute shorter, as the "false" ending fadeout is presented as the track's true ending (and it thus omits the closing scream of "I got blisters on my fingers!") The significance of these differences will depend on the level of one's Beatles fandom; of course, those shelling out for the In Mono box will likely enjoy poring over the details.
Paul
