In a thread I started about things hard to find, I mentioned the original Fantasound release of Fantasia (when I meant to refer to the original Roadshow edition with Deems Taylor's voice and Sunflower not cropped, plus Fantasound mixed for the DTS-HD MA ) However someone said the laserdisc had simulated Fantasound (maybe not the real thing but close) thanks to Dolby Pro Logic but not sure about the VHS. Well the Dolby Surround logo appears on the back cover of the VHS so it must have been mixed from the same master as the laserdisc.

Fast forward to just several minutes ago when a family member went through her old tapes and donated them to me yesterday. I got to open the shopping bags today and once the VHS of "Jumanji" broke, I thought my VCR was doomed. I cleaned the head with a head cleaning tape just to make sure it was just that one movie, and then I picked Fantasia. After the opening credits, I was shocked to hear Deems Taylor's voice in amazement. And not only that, with my A/V receiver set to Dolby Surround manually I can safely say this is the best release for a budget audiophile. I mean, the music bounces from speaker to speaker.

Sure Sunflower is cropped and this is a reissue with reissue titles (including the 1990 Walt Disney Pictures logo and end credits), but this VHS is a must-have if you want to hear Deems Taylor's voice REALLY BADLY and want a Fantasound-like soundtrack.

The setup is simple:

4 Head Hi-Fi Stereo VCR with Dolby Surround settings
Speakers: 4-7 is plenty, subwoofer optional
A/V Reciever with Dolby Surround/Pro Logic as an option for decoding
TV (Any TV from analog to 4K (maybe 8k) should do fine)
An authentic copy of the 1991 Fantasia VHS (it shouldn't be too hard to find secondhand if nobody you know bought it)
Any A/V cables (HDMI works too if a DVD/VCR has one)

Set it up, then when the output works push the Dolby button and pop it in. It may not be thrilling at first from the opening, but then when the actual film starts prepare to be mindblown. I'm sure you older animation buffs probably were.

Now that I told you my experience, how in the world did Disney make it like Fantasound for the VHS and Laserdisc if the original tracks were lost?
If you want to get into the nitty-gritty of what Fantasound actually was, here's a super technical contemporary article: 

Concerning how Disney were able to recreate Fantasound, this is the most succinct article I could find to answer your question:

Essentially, the earliest surviving stereophonic sound master (a 1955 4-track magnetic recording off a "Fantasound quad print") was remixed and restored for the 1990 theatrical re-release (and the subsequent VHS and Laserdisc edition) in an effort to bring it closer to what Fantasound would have been like based on the seemingly comprehensive documentation in the vaults.

What seems a little unclear to me is whether the 1955 magnetic recording would have contained the full Deems Taylor narration or whether the quad print source still survives today. I haven't been able to thoroughly compare subsequent DVD/Blu-ray restorations so I can't say whether they have "improved" over Terry Porter's mix.

On a side-note, a "SuperScope" IB Tech from the 60s with 4-track magnetic audio does exist in a private collection. This in theory would probably provide some insight into what the 1955 magnetic recording master would have sounded like, "pre-restoration".
Interesting reads!

While I am going a bit off-topic (and if I tried to provide any more information, I would've repeated what has been said multiple times about this topic), I believe that the shorts originally produced in CinemaScope, like Fantasia, were screened in theaters in stereo (the Rarities and fourth Donald Treasures sets include most of these shorts with mono soundtracks). Could there be any way these shorts could be reconstructed in multi-channel sound (if they truly were released that way)?