This is an exceprt from an interview with Dave. It was on the In The Studio radio program where they choose an album and talk with the people who made it.
It's a bit of a joke. We started off once, and we put all the tracksdown without any noise reduction on them, but using these things called keypexes (sp?) which are noise gates which would turn the tracks on when we were using them and off when we weren't using them. Just cut out the hiss between the moments, you know. And like the Dolby system, which is a general noise reduction system which is in operation all the time. And then -- this is a period of very heavy technical advancements rapidly happening. During that period of time the Dolby system became quite wide spread, and they got them in at Abbey Road, and we actually had all the tapes copied. All the master tapes were copied onto -sixteen track non-Dolby onto sixteen track Dolby. So all the masters are second generation from the word go. It's amazing what you can do with sound. Technically speaking, every rule in the book was broken on that. And people think it's a kind of an audiorile record. Wonderfull (chuckle). And it shouldn't really be that way (interviewer laughs).