A fair amount of unreleased AOTC music found its way into TFU and I'm guessing GM is going about trying to encorporate those snipets into his set.

I'm attempting to make an AOTC Complete Recordings set that contains the official release, the score as William's intended it and then a complete score, and am currently in the process of including the new TFU material myself. Mine differs from GM's in that I'm trying to present the music as it is played in the film i.e. with all the Burtt edits included (I know...shoot me now).

One of the most unpleasurable edits I did was trying to reconstruct the conveyor belt music used in the film from about 15 different tracks from TPM and AOTC... Burtt well and truly hacked away at that music!