The Sydney Morning Herald and AZ Central both have interviews with Allen Rouse, head engineer on the upcoming Beatles remasters, who talks about the delicate balance between improving sound and changing it.
Some key excerpts:
Has A Day in the Life been improved, for example, by removing the squeak of the piano stool that punctuates the ultimate chord of doom? Heaven forbid, Rouse says.
"We agreed at the onset we would only remove things that were technically related. If it had anything to do with the Beatles' performance — breaths, coughs, squeaky bass drums, squeaky chairs — they stayed."
..."The Beatles spent upwards of two or three weeks mixing Sgt Pepper in mono. The stereo was done as an afterthought by George (Martin) and (engineer) Geoff Emerick — regrettably forgetting some of the things they had done on the mono mixes," Rouse says.
...one of the things we did agree that we would be very cautious about is limiting, which is where you make them as loud as you can. That's the common process of most recordings today - make 'em as loud as possible so that they're as loud as the last band. We agreed that we would not do that, because these are 40-year-old recordings and they don't deserve to have the dynamics of their songs destroyed. At the same time, we felt, for the stereo master, that a small amount of limiting that didn't destroy the dynamics would be acceptable, so they are a bit louder.