Apple Soundtrack Pro 2 - Manual (Page 307)

Chapter 9 Mixing Surround Sound 307
Converting a Stereo Mix to 5.1 Surround
Many post-production projects require both a stereo mix and a surround mix. This
section reviews some best practices for converting projects from stereo to surround.
You can reverse the steps below to convert a project from surround to stereo.
Important: When you switch between stereo and surround panners, panning
automation (envelope) settings are not automatically copied over to the new panning
mode. Volume information is automatically copied over between stereo and surround
panners. The recommended workflow for making a surround version of a stereo mix is
to maintain at least two separate versions of the project: a stereo version and a
surround version.
To create a separate copy of your stereo mix for surround mixing:
1 Choose File > Save As in your stereo project to save a separate copy.
In the dialog that appears, indicate in the filename that this is the surround version.
(For example, “My Great Mix_surround.”)
2 Use this copy of the project to make all the necessary surround panning adjustments.