Any appointment at Abbey Road still involves walking over the most famous pedestrian crossing in popular music. And the history of the north London studio hangs heavy in the air when the meeting is with the engineers who have just finished digitally remastering all the original Beatles albums, from Please Please Me through Abbey Road.

Borrowing a phrase from one of those engineers, project coordinator Allan Rouse says wryly that his seven-member team has spent the last four-and-a-half years fiddling with the crown jewels, a phrase that could induce alarm in audiophiles. But Rouse and his colleagues have years of experience with the Beatles masters among them, and they approached the most famous 525 minutes in recorded-music history with meticulous respect.

Rouse, who joined EMI straight from school in 1971, began his career working with Beatles engineer Norman Hurricane Smith. Recording engineers Guy Massey and Paul Hicks worked on the 1995 Anthology DVD set, while Rouse and others oversaw the 5.1 surround sound and stereo mixes of the 1999 Yellow Submarine reissue.

Even so, they knew that one intrusive piece of sonic tweaking could infuriate hordes of fans -- many of whom have a relationship with Beatles albums that borders on the obsessive.

There were seven of us involved, so as not to put this huge amount of pressure on the shoulders of one individual, Rouse says candidly. Sean Magee, who worked with Hicks on the mono versions of the remasters, adds, You have to switch into work mode. You basically do it as you would any remastering job, with due reverence to what went before.

Rouse passionately defends the decision to go back to master tapes that were last reissued in 1987. There was nothing really that wrong with the '87 (releases), he says. In some ways, however, they're no longer up to today's standards. It's a long overdue overhaul. The minute the CD got invented, everybody thought it was adequate to get the master tape out and put it onto CD. Remastering was something that happened maybe a decade or so later.

Many of the changes Rouse and his team did make are less the result of creative fiddling than superior equipment. Today equipment exists that didn't exist then to (handle) some of the things we decided we wanted to tackle, he says. With a tiny bit of help here and there, they're greatly improved.

Most of those improvements are subtle, and the engineers chose not to apply the dynamic compression found on some recent remasters. Our tweaking, in terms of EQ, is quite subtle, he says. There's upwards of 20 tracks, within the stereo (remasters), where we haven't done anything. There's a large number above that where it's very small amounts of EQ. Maybe you're trying to help the drums, (for instance, if) Ringo (Starr's) snare isn't cracking through.

Rouse says the team tweaked a small number of bad edits, dropouts and, more importantly, sibilance, microphone pops and electrical clicks. Some probably went unnoticed. One that casual listeners might have heard was the pop in John Lennon's vocal on I'm a Loser, now corrected.

We'd already agreed that if we thought (a mistake) was in any way connected with the performance, we weren't going to touch it, he says. Breaths, Ringo's squeaky bass drum pedal, the squeaky chair at the end of 'A Day in the Life,' coughs, (McCartney's) 'f*ck' in the middle of 'Hey Jude' -- all of these little things were going to remain.

First, Massey listened to each track up to three times and made a list of what needed to be tweaked on each album. Then audio restoration engineer Simon Gibson made the necessary change, so that it didn't affect the integrity of the recording.

Rouse and Magee played Billboard some before and after comparisons of how the new masters sound compared with their 1987 equivalents. And from the harmony vocals in Hey Bulldog and Goodnight to the backward cymbal in While My Guitar Gently Weeps, many sounds are crisper and more vital. Of course, many listeners will hear these new albums not on the high-end speakers at Abbey Road but on car radios or--worse yet from a sonic perspective -- ripped MP3s.

The way people listen now is on equipment that quite frankly is inferior, Rouse says. I don't think anybody in this building or any other studio in the world ever changed their attitude about trying to provide the best possible sound, but nobody's hearing it. It's a crying shame. I don't really know how you can change that apart from educating people that what they're hearing is only part of what's there.

If and when the Beatles catalog comes to iTunes, Rouse says, the team could decide to make further tweaks. We haven't looked into it, but let's say for instance you had to create a slightly different EQ'd master to make it acceptable for this method of playback, he says. So it goes up on iTunes and you can put it on your iPod or whatever and it sounds better. What happens then if somebody decides -- as I'm sure people must do -- to burn a disc, they've got decent hi-fi and they play it on that? You've now created something that isn't the best way of representing it, so you're putting out two masters. That worries me, I've got to admit.

Rouse declines to comment on the remastering budget but hints that it inevitably ran beyond the initial number. Every time we do a Beatles job, I have to budget for it, he says. An estimated 25,000-pound budget ($41,000) for the 1999 Yellow Submarine mixes ended up being half of the real cost.

You get it as right as you can, Rouse says, but I still have an attitude (of), 'OK, I've gone over. So what? It's the Beatles.'