Since the late 1920s, the Silly Symphonies series of short films had been extremely successful for the Disney studios. These little movies were early combinations of music and animation, usually telling a story or simply representing the theme of the music. After a decade of producing them, Walt was ready to take this idea further. He wanted to make the ultimate Silly Symphony, and he knew just which of his stable of characters he wanted as its star.

The Sorcerer's Apprentice was to have been longer than most of the Silly Symphonies, and would have featured the housecleaning mishaps of that most loveable dwarf, Dopey. However, Dopey was soon removed from the film and it wasn't long before Mickey Mouse stepped into the role for which he's become most famous. The film was still going to be made as a stand-alone short though, but a chance meeting changed that.

It's difficult to imagine now just how big a star Leopold Stokowski was in the 1930s. I guess he was the biggest rock star of his day, as famous for his partying and love interests as for his music. His orchestral conducting and personality breathed new life into the rather stuffy world of classical music.

Walt ran into the conductor when they were both dining at the same Beverley Hills restaurant and, after expressing their admiration for each other's work, Disney casually mentioned his latest planned short based on the Sorcerer's Apprentice. Stokowski immediately showed an interest in conducting the piece for the film, and suggested a few other compositions that Walt might want to consider putting images to. This fortuitous encounter would give birth to The Concert Feature, the movie we know today as Fantasia. While the Sorcerer's Apprentice was soon completed, Mickey's greatest role was forced to sit on the shelf for another two years while the studio worked on the rest of the movie.

Upon release in 1940, Fantasia featured eight distinct animated musical sections, but not all of them were produced as originally intended. For example, everyone remembers the Nutcracker Suite portion of the film with its delightful dancing mushrooms. But how different would the movie's interpretation of Tchaikovsky's music have been if the animators had stuck with their original idea of using dancing lizards instead of the mushrooms? And how much less of an emotional impact would have been made by actually seeing Sorcerer Mickey violently hacking down the first broom with his axe (as in the version that was originally animated), rather than viewing the sequence in striking silhouette?

Another change was the addition of Beethoven's Pastoral Symphony to the Greek mythology segment of the movie. Originally, the Centaurs and winged horses were to have performed to Pierné's Cydalise et le Chevre-Pied, an altogether less well known piece.

These amendments made quite a difference to the version of the film that eventually made it to cinema screens, but of course, these were only the sections of the film that made the final cut. There were many other ideas that didn't make it that far.

Adventures in a Perambulator by contemporary composer John Alden Carpenter was to be played alongside a cartoon trip to the park. The very stylised drawings would all be seen from the baby's point of view, as if the cinema audience were looking out of the baby carriage. Another idea to feature cute babies was the Baby Ballet, set to Chopin's Bercuse. This would have shown the little cherubs dancing and bathing.

Ride of the Valkyries was to be a straightforward representation of Wagner's celebrated composition about the daughters of Wotan escorting the souls of warriors to Valhalla. As if this heroic vision wasn't enough, there was briefly a plan to include characters and partial story from Tolkien's Lord of the Rings prequel, The Hobbit into the same musical section. Another possibility for Fantasia that was partially produced, The Swan of Tuonela, shares a similar inspiration with the Wagner piece. It is however extremely different musically. This gentle air conjures up visions of the mythological swan that supposedly carries the dead to Tuonela, the Finnish name for the underworld.

Debussy's Clair de Lune almost made it into the final version of the movie. This beautifully animated sequence was later set to the tone poem Blue Bayou, and with this different music appeared in the 1946 compendium movie Make Mine Music.

Other pieces that were considered but never made the cut included

Stravinsky – Reynard
Stravinsky – Petrouchka
Stravinsky – The Firebird
Richard Strauss – Don Quixote
Richard Strauss – Till Eulenspiegel
Prokofiev – The Love for Three Oranges
Weinberger – Schwander the Bagpiper
Kodály – Háry János suite
Wagner – Pilgrim's Chorus
Mozart– The Magic Flute
Berlioz – Roman Carnival Overture
Holst – The Planets

Disney and Stokowski even considered including a version of the children's song Pop Goes the Weasel.

Walt intended Fantasia to be reissued every year with new segments gradually replacing the old favourites. Cinemagoers would be able to see beforehand what the programme was for tonight's screening of Fantasia, which sections had been inserted and which had been removed. Audiences were used to seeing a programme of what was going to be played at orchestral concerts, and Fantasia was to be a logical progression of that experience. Walt thought that the public was ready to embrace this more adult animation as a new art form that would elicit a purely emotional response, just like attending a symphony concert.

Unfortunately, he was wrong.