Disney settled on the film's concept as work neared completion on The Sorcerer's Apprentice, an elaborate Silly Symphonies short designed as a comeback role for Mickey Mouse, who had declined in popularity. As production costs grew higher than what it could earn, he decided to include the short in a feature-length film with other segments set to classical pieces. The soundtrack was recorded using multiple audio channels and reproduced with Fantasound, a pioneering sound reproduction system that made Fantasia the first commercial film shown in Stereophonic sound.