The mix of the undubbed master on all releases contains no backing vocals, only the backing track.
The undubbed masters on Our Memories Of Elvis weren't really the pure undubbed masters. They
were the fully overdubbed or regular masters but
with certain instruments and backing vocal channels
removed or stripped down.
All outtakes and masters used on the Sony 3xCD
set Elvis At Stax have been completely remixed
and remastered from scratch.
In March of 2007, Sony decided to go through all of Elvis' masters. They retransferred everything and remastered all tracks including repairing as many clicks, pops, bad edits and dropouts as they could. They have used these newly mastered recordings on their new releases since 2007 including budget soundtracks, Legacy releases, the 30 disc Complete Elvis Presley Masters collection and the Franklin Mint package.