Originally posted by: ocpmovie
...you can shuttle back and forth between two versions of the 70mm soundtrack...

???
AFAIK there was only ever one version of the original 70mm soundtrack, and I would be very surprised if the creators of this DVD were able to get their hands on an original 70mm print, extract the 6 tracks (which I believe were in "4.2" surround format) and remaster to 5.1 AC-3.

More likely the tracks are from the original Dolby Surround from the 35mm prints (used in the first laserdisc transfers), the digitally remastered mix from 1985 or the THX certified mix from the 1993. The latter two I think used parts of the 70mm 6-track mix.