The OT had made some discussions about the specific changes in this alternate cut.
http://originaltrilogy.com/topic/ESB-70mm-Soundtrack-1980-in-theatre-recording/id/12501/page/1
https://originaltrilogy.com/topic/Hopefully-the-last-70mm-vs-35mm-ESB-audio-differences-thread/id/14128/page/1
http://originaltrilogy.com/topic/70-mm-print-of-the-Empire-Strikes-Back-Differences/id/2321/page/1
Someone did a recreation of that alternative ending on YouTube.
https://www.youtube.com/watch?v=cmbl8tLOfFE
The audio in that video is a vintage In-Theater recording of a screening from that alternate cut.
Details about that audio recording can be found here:
http://wideanglecloseup.com/starwarsaudio.html