Well I didn't actually say HD space, I meant RAM. But even so, since you bring it up: Garageband running on a Mac (just like Logic and many other apps) allocates free HD space to process information.
Yep, that's why reducing bit depth won't really impact on the size of the project, the files are kept on the HD and not in RAM and are (pre) loaded when needed.
Yep, that's why reducing bit depth won't really impact on the size of the project, the files are kept on the HD and not in RAM and are (pre) loaded when needed.