The audio can be a bit more difficult as it depends on the original recording process, and the masters that might be laying around. Considering how old Casablanca is I wouldn't be surprised if it was a Mono track. In those instances they typically split it into two channels to give the impression that something is "surround sound". It really all depends on how the original audio was recorded and the condition of the masters but my guess is Casblanca is Mono 2.0 for DVD, Blu-ray or any remastered prints playing in theaters. With companies that are very good at doing film restorations (like Criterion and Kino) they will usually remaster everything and split up the audio into separate channels if possible. It is a very labor intensive process, and is a big reason why it takes so long for them to put out discs and the typical high cost of them. It probably isn't possible for them to do 7.1 in the vast majority of cases, but true 2.1 is pretty common and typically sounds very good and even Mono 2.0 can sound pretty impressive when done right. But we are talking films made pre-1960 or so. By the 80's pretty much everything was recorded so you could remix it into absurd numbers of multiple channels. Also, to clarify, remastering audio doesn't really mean making the soundtracks sound better, but it is about making the film sound as how the director originally intended. Films that were recorded in Mono will always be 2.0, and it is simply a matter of making that 2.0 sound as good as possible for home theater. It may not seem right, but Casablanca in Mono 2.0 would sound much better then in 7.1. So I guess the answer is if they can make something 7.1 nowadays they will, but they won't artificially turn a Mono soundtrack into 7.1. Hopefully Robert steps in and explains this better then I can.