Well, thanks to hairy_hen and The Starkiller's Guide to the Star Wars Mono Sound Mix, I was able to cobble together a list of at least some of the differences between the different tracks for each film. For the mono track, I went ahead and listed EVERY difference I came across, but I don't know if this level of detail is wanted/needed.
Everyone, please feel free to add/edit/correct anything as needed.
STAR WARS
1977 70mm Six-Track Reconstruction (Dolby Digital 5.1)- 1993 audio mix (sourced from 1977 stereo and six-track mix)
- Upmixed to five channels
- LFE bass from 1993 mix and 2004 Special Edition
1977 Theatrical 2.0 Surround
1977 Theatrical Mono
Notable features
- Different alarm in background aboard the Tantive IV Blockade Runner
- Different voice for Aunt Beru
- R2-D2 beeps upon the discovery of the slaughtered Jawas (also featured in the 2004 mix)
- Sounds made by snake-like cantina patron (opposite Wolfman patron) are extended (also featured in the 2004 mix)
- Chewbacca growls as stormtroopers pass him and Han in the cantina (also featured in the 2004 mix)
- Different voice/lines used by stormtrooper while searching for C-3PO and R2-D2 in Mos Eisley
- Different sound effects for 3D chess game
- Chewbacca makes an extra growl while playing 3D chess (also featured in the 2004 mix)
- 3D chess monsters make different noises
- Deceleration sound heard when Millennium Falcon exits hyperspace near the Death Star
- Radio frequency sound effect heard after Han says, “Chewie, jam its transmissions”
- Different sound effect of Millennium Falcon being caught in the Death Star’s tractor beam
- Contains C-3PO’s explanation of the tractor beam
- Different voice/lines when Governor Tarkin is informed of the detention block security alert
- Different foley and ADR during trash compactor sequence
- Different take of C-3PO saying, “What? Use the comlink? Oh my, I forgot, I turned it off”
- Different cho effect in Death Star chasm
- Contains the line “Close the blast doors”
- Additional gun turret sound effects heard while Luke prepares for TIE fighter battle aboard the Millennium Falcon
- Different take of Luke saying, “So, you got your reward and you’re just leaving then?”
- Porkins does not scream
- Different voice for Death Star countdown
- Luke says “Blast it, Biggs,” not “Blast it, Wedge”
- Battle of Yavin radio chatter is undistorted
1985 Home Video 2.0 Surround Remix
1993 Home Video 2.0 Surround Remix
Star Wars Isolated Stereo Score
THE EMPIRE STRIKES BACK
Alternate Dolby Digital 5.1 "version 1" Remix
- 1993 audio mix
- LFE bass from 2004 Special Edition
Alternate Dolby Digital 5.1 "version 2" Remix- 1993 audio mix
- LFE bass from 2004 Special Edition
Notable features
- Snowspeeder crash sound from 1980 mix
- Boba Fett’s departure from Bespin uses Williams’ unedited score from 1997 mix
Alternate Dolby Digital 5.1 "PURIST" Remix
- 1993 audio mix
- LFE bass from 2004 Special Edition
Notable features
- Snowspeeder crash sound from 1980 mix
1980 Theatrical 2.0 Surround
Notable features
- Snowspeeder makes a sound when it crashes
1993 Home Video 2.0 Surround Remix
Notable features
- No snowspeeder crash sound
Empire Strikes Back Isolated Stereo Score
RETURN OF THE JEDI
Alternate Dolby Digital 5.1 "version 1" Remix
- 1993 audio mix
- LFE bass from 2004 Special Edition
Notable features
Alternate Dolby Digital 5.1 "version 2" Remix
- 1993 audio mix
- LFE bass from 2004 Special Edition
Notable features
- Obi-Wan’s appearance on Dagobah uses Williams’ previously unused music
- Vader’s defeat uses music from 1977 35mm stereo mix
Alternate Dolby Digital 5.1 "PURIST" Remix- 1993 audio mix
- LFE bass from 2004 Special Edition
Notable features
- Vader’s defeat uses music from 1977 35mm stereo mix
1983 Theatrical 2.0 Surround
1993 Home Video 2.0 Surround Remix
Return of the Jedi Isolated Stereo Score