The remastering project for both mono and stereo versions was led by EMI senior studio engineers Allan Rouse and Guy Massey.

Stereo recordings were a fairly new concept for pop music in the 1960s and did not become standard until nearly the end of that decade.

Pepper's Lonely Hearts Club Band, all the mono mixes were done together with the Beatles themselves, throughout the recording of the album, whereas the stereo mixes were done in only six days by Abbey Road personnel George Martin, Geoff Emerick and Richard Lush after the album had been finished, with none of the Beatles attending.

[13][14] Less than two weeks before 9 September, many other online retailers announced the selling out of units from their inventories, including the Canadian Amazon.ca site.

[15] EMI announced on 3 September 2009 that more mono boxed sets were to be pressed due to high demand from online pre-orders.

The same holds true for the songs "The Ballad of John and Yoko", "Old Brown Shoe" and the single mix of "Let It Be", which were also omitted.

Abbey Road and Let It Be were issued in the UK in mono on reel-to-reel tape and on LP in Brazil and other countries but, again, only as fold-downs from the respective stereo versions.

However, the mono mixes of "Don't Pass Me By" and "Helter Skelter" had been previously issued in the US in 1980 on the Capitol Records Rarities compilation album.

The set debuted at number 40 on Billboard's Top 200 chart and the magazine reported that 12,000 copies were sold in its first week of release.

[17][18] In Japan, it debuted at number 10, selling over 20,000 copies in its first week on the Oricon album charts.