LONDON , England ( CNN ) -- They were entrusted with gold . The Beatles , shown here in 1964 , left behind a wealth of material , which was carefully handled by EMI 's engineers . When the Beatles ' longtime record label , EMI , decided to remaster the Beatles ' music , they gave the raw material to a handful of men . Among them were EMI engineers Allan Rouse , the project coordinator , and Sean Magee . Rouse , in particular , was familiar with the tapes . He was the person who had copied them from their original analog form to digital as a safety backup in 1991 . He 's since worked on the Beatles projects `` Live at the BBC , '' `` The Beatles Anthology '' and `` Let It Be ... Naked . '' CNN 's Jim Boulden was given the chance to sit down with Rouse and Magee . The following is an edited and condensed version of the interview . For the complete interview -- including some technical details -- click here ( .pdf file -- requires Adobe Acrobat ) CNN : Why was this project taken and why so long ? Rouse : It was started 4 1/2 years ago and it has taken over that period of time about a year to do the whole thing . On average about two weeks per album . Explore a timeline of the Beatles over the decades . CNN : What does this allow you to do that you could n't have done to these songs before ? Rouse : When they were originally transferred to CD in 1986 , digital technology was in its infancy and the gap of 22 years has allowed for a great increase in that technology . So the transfers are far superior now and that was before we actually did any work to them . In addition to that , we had decided that we wanted to remove or improve technical faults within the recordings that could have been a bad edit , a dropout , vocal sibilance , vocal pops . Things that were directly related to the technical recording rather than the human recordings , so in other words we have n't taken out breaths or little coughs or squeaky chairs or Ringo 's occasional squeaky bassdrum pedal . CNN : Tell us about the process ? And that is where you came in [ Sean ] . Magee : The first part of the process is choosing what equipment you are going to use to do the image and the transfers . ... And then after choosing ... everything was transferred track by track into protocols , making sure the tape heads were nice and clean and the tape speed was constantly monitored , so the best possible transfer could happen . Then Guy Massey , who did all the transfers , went in with the restoration engineer -- a guy named Simon Gibson -- they then looked at all the various ticks , pops , sibilance and sorted all that out . ... That now becomes your master tape and that 's when we started , really . CNN : Each [ song ] had its own challenges ? Magee : Absolutely . CNN : What were the differences ? Would it take a week on a song , six months on a song ? Magee : More likely four or five hours on a song . On average we took about two weeks per album . But sometimes it might be three or four hours on a song , it might be 10 minutes on a song . CNN : How much involvement was there from the Beatles themselves ? Rouse : They were n't involved in the process . Obviously they have to sign off on it . So when we finished it , we provided them with a copy of every album . But the process was over such a long period of time and it would be very complicated to have involved them anyway . I 'd like to think they have some trust in us because we 've done numerous other jobs for Apple . CNN : And you have n't heard back and that is good news ? Rouse : Basically , if the phone does n't ring , that is good news , yes . CNN : There always will be people who say ... you are messing with something in the original -- . Rouse : Playing with the crown jewels . CNN : There probably will be a critic out there that will complain . Rouse : Yes . CNN : But you are clearly pleased with your outcome ? Rouse : Yes , I think , actually before we even started work on them , by doing an [ equalization ] ... they actually sounded better and I think quite frankly , probably the closest they have sounded to the original masters , than they have done ever before . CNN : Anything surprise you by going through this whole process ? Rouse : Probably the only surprise is that when I started buying the vinyl in the '60s , I bought stereo , so I had never heard mono , and to be honest with you it was actually quite a fascinating experience to sit and listen to , particularly `` Sgt . Pepper '' in mono . I mean , up until `` Sgt . Pepper '' and beyond , up to the White Album in fact , the monos were considered to be the real masters in the sense that in the '60s Britain was n't up to speed , we had n't quite got to stereo . The only people who really had stereo in those days were people who could afford it and invariably that meant they were listening to classical music or middle-of-the-road music . ... To suddenly hear the monos , I don¹t think , in fact , I had listened to the mono `` Sgt . Pepper '' in all the years I have been doing Beatles work . Until this particular time . CNN : The press release says you took out bad edits . I did n't know there would have been bad edits in the original Beatles . Rouse : There was n't many to be honest , I mean it was just an issue that we could deal with now . There were a few songs where they had created it over two takes and they wanted to use a part of one take and a part of another , and sometimes the edit was n't as good as it could be . In some cases we could n't do anything about it , But if we could we would try and smooth it over so it was n't so obvious . CNN : Did you achieve [ what you were going for ] ? Rouse : I think that 's up to other people to judge , is n't it . ... It was a team effort . And I think that was the most important thing , one person wasn¹t involved in just doing the one thing . In fact it would have been ... CNN : Awful ? Rouse : ... it would have been unfair . CNN : Was there a time pressure as well ? Rouse : No there was no time pressure . There was a possibility of them coming out sooner , but we were way up anyway by that point . That got extended . I think that when EMI put the press release out , we all did a double take and thought , `` Oh my God , they 're coming out now . We can¹t do anything about it now . Should we go back and start again ? '' There was some fear and trepidation at that point . Realizing that after four years not quite knowing when they were gon na come out , to suddenly be told `` That 's it , no more time lads . You 're finished . '' iReport.com : Share your review of the Beatles box sets . CNN : And now they are ready for digital downloads if we get to that point . Rouse : They are . If they do .
Engineers spent more than four years on Beatles catalog remastering . Group strived to stay as close to originals as possible , yet clean up flaws . Score: 6