I think what people need to understand is how much work actually goes into some of these demos... Like others have already said they use all sorts of programs for making them. They sound so good because they are produced in a top quality professional studio with highly trained techs and musicians. Just about a year ago I spoke with a Yamaha tech about a problem I was having with a keyboard, and I asked him would I ever get the board to sound as good as the demos.. and he said, "with the proper software and in depth knowledge on music theory and structure, anyone can get their keyboards to sound like the demos.." He also stated that one of the main reasons these demos sound so good is because the techs are also masters of step recording.

Squeak