On page 515 of Volume 9 of the Walt’s People series, we find the following quote from Tom Sito concerning the differences in the recordings for the scores of Fantasia and Fantasia 2000:
Then the other issue people had was when you work in the original footage, because our film was going to be done in the modern screen format of 1:85. And it’s also six-track Dolby digital stereo and the original Fantasia, even restored, still was in the 1:33 original aspect ratio, the old cinema aspect ratio, plus they had all kinds of problems with the stereo.
In 1949 they transferred the original tracks from the original recordings on the nitrate strip. And they went to magnetic tape. The new invention in the 1940s was magnetic recording tape, so they wanted to go to mag-track on it, and the best labs in the world at the time were at NBC TV. So they wanted to transfer the Fantasia tracks to magnetic tape, but in so doing they transferred them along telephone lines and by doing that they lost a lot of the high and low registries, some of the high notes and some of the low notes. And it has always been part of the problem when they digitally re-mastered the sound: It always loses a little something, because some of the parts of the performance were lost in the recording. The preservationists go crazy trying to figure out: They had scientists working on it full-time, like John Carnaughan and Alex Rannie. It was interesting, because every couple of weeks they would have us into the Studio and they would say, “I think we licked it. Okay, let’s play the modern stuff and then let’s play the old stuff,” and then they would say, “Can you hear the difference?” We would say, “Yeah, you can hear a difference.” [Laughs] They still sounded different. To their credit, they were not going to make the mistake of getting rid of Stokowski’s soundtrack.