The original 6-track mix appeared first on LaserDisc and then later on the 1998 MGM DVD and most recently the 2018 blu-rays. Overall, the LaserDisc (I have PILF-2510 from 1997) sounds the least tampered-with, but the DVD is similar. The blu-ray's original mix has a varying amount of noise reduction applied throughout, as well as some EQ that gives the dialogue more body and (more in line with modern recordings) but makes everything else--music especially--sound thicker and less airy.
I'm actually rather disappointed by the theatrical 6-track mix itself. Some of the musical sequences are doused in reverb and sound distant and garbled. The Blue Danube seems like it was mixed from a mono source - each channel differs only by EQ. (These sequences would probably sound better if every speaker just played the content of the centre channel.) The end credits music sounds especially bad in this respect.
Still, the remix has audibly more noise reduction overall, especially the Star Gate sequence which sounds dull next to the LD.
In terms of pure fidelity, the 2.0 track on the 1997 LDs is comparable to the AC-3 6-track. The earlier ML103104 disc from 1993 (and the Criterion LD*) is thinner and less detailed.
There's also a Cinema DTS disc that was produced for the ~2007 release, but I don't think it sounds noticeably different than the remixed track on the blu-rays.
Left:
Right:
Surround left:
Surround right:
LFE:
