A couple questions about the sound mix, now that we’re on the subject.

Could someone refresh my memory as to the difference with Threepio’s infamous tractor beam line? When it cuts to the animation on the screen do you simply hear him say nothing in one version and “a power failure at one of the terminals will allow the ship to leave” in the other?

My other question is about the monomix and just why it was put together in the first place. Wasn’t the theory about certain theaters needing the monomix debunked or am I remembering wrong? I thought the stereo optical track would’ve been backward compatible with all the existing sound systems in use at the time, mono or otherwise, but I could be wrong.