About halfway through the cantina scene I watched this evening, all the background cantina noise disappeared really suddenly - up to then, the film had been rapidly cutting back and forth between color and black and white, and then it was mostly black and white, only occasionally becoming color. Afterwards, the only sounds I heard were when someone would talk, and it would cut in all of a sudden, almost sounding like the way voices sometimes cut in and out on a cell-phone. This lasted all the way up to after the stormtroopers arrive. The only reason it stood out to me is because, like you said, the rest of the film is chockfull of sound. I just didn't know if a continued audio track of the background cantina noise just didn't exist.
I hope I don't sound like I am complaining about this in any way. I was just wondering if there was just no existing audio of the background cantina noise after a certain point, or what. I understand completely that the black and white portions are from a detoriarated cut (I assume the same cut that featured the treadwell?) - I just didn't understand why the background cantina noise disappeared so suddenly.