Mating the concept of its 1940 film Fantasia with the modern IMAX treatment, Disney has given birth to a sumptuous, giant-screen love child. Seven new animated segments, along with the original The Sorcerer’s Apprentice, featuring Mickey Mouse as a magician trainee, are fueled by music from the Chicago Symphony Orchestra. Introductions from such hosts as Steve Martin, Bette Midler and Quincy Jones provide the feeling that something wondrous is to follow. They do not deceive. The marvels include an ecological fable about the destruction and rebirth of nature, whales that soar through frozen seas as well as the air, and a day in Depression-era Manhattan.