This is a 4 CD set that Disney was going to release to mark the 40th anniversary of the World's Fair but cancelled apparently because of rights issues concerning some of the music related to the Ford Pavilion. The tracks though have circulated among Disney collectors and you can usually find them on IRC at disney-central. Each CD is devoted to one of the four Disney pavilions at the Fair. Among the gems are the original narration tracks for "Great Moments With Mr. Lincoln" (not the old 7 inch souvenir record), isolated underscore, demo versions of "Carousel Of Progress", original session recordings for "It's A Small World" and Walt's narration for the 1965 season on "Ford Magic Skyway" (not to mention outtakes of Walt flubbing his lines)
The set is well worth having if you can get it via trade (as I did) or by IRC. A must for both Disney and World's Fair buffs.