The re-mastering process commenced with an extensive period conducting tests before finally copying the analogue master tapes into the digital medium. When this was completed, the transfer was achieved using a Pro Tools workstation operating at 24 bit 192 kHz resolution via a Prism A-D converter. Transferring was a lengthy procedure done a track at a time. Although EMI tape does not suffer the oxide loss associated with some later analogue tapes, there was nevertheless a slight build up of dust, which was removed from the tape machine heads between each title.
From the onset, considerable thought was given to what audio restorative processes were going to be allowed. It was agreed that electrical clicks, microphone vocal pops, excessive sibilance and bad edits should be improved where possible, so long as it didn't impact on the original integrity of the songs.
In addition, de-noising technology, which is often associated with re-mastering, was to be used, but subtly and sparingly. Eventually, less than five of the 525 minutes of Beatles music was subjected to this process. Finally, as is common with today's music, overall limiting - to increase the volume level of the CD - has been used, but on the stereo versions only. However, it was unanimously agreed that because of the importance of The Beatles' music, limiting would be used moderately, so as to retain the original dynamics of the recordings.
When all of the albums had been transferred, each song was then listened to several times to locate any of the agreed imperfections. These were then addressed by Guy Massey, working with Audio Restoration engineer Simon Gibson.
Mastering could now take place, once the earliest vinyl pressings, along with the existing CDs, were loaded into Pro Tools, thus allowing comparisons to be made with the original master tapes during the equalization process. When an album had been completed, it was auditioned the next day in studio three - a room familiar to the engineers, as all of the recent Beatles mixing projects had taken place in there - and any further alteration of EQ could be addressed back in the mastering room. Following the initial satisfaction of Guy and Steve, Allan Rouse and Mike Heatley then checked each new re-master in yet another location and offered any further suggestions. This continued until all 13 albums were completed to the team's satisfaction.
