To be more specific with Horizons, the 'GBBT' theme was played in *five* scenes...with three scores.
(1) Inventions
Immediately after going through a bunch of lighting up clouds and hearing the 'if we can dream it' sparkly music, we see a bunch of animated inventors fading in and out on a screen. Here, an airy, accordian version of Great, Big Beautiful Tomorrow begins. It's not the exact tune...but it syncs perfectly with the song.
(2) Jules Verne
The same music continues...
(3) Man in the Moon
The same music continues...
(4) Robida's Paris
The GIANT painting - here, the old music is identical in tune, but now, instead of an accordian style, it goes full-fledged into orchestra. This version was slowed down in pitch and tempo and was labeled "Great Big Beautiful Tomorrow - Jules Verne Version" on Walt Disney World Forever...but now we know this is not the case. It was one of my favorite loops in the entire show - very unique!
(5) Easy Living/Art Deco
This scene, with the robots, the family, the man with his hair being clipped has a totally different tune - it's the actual themesong being sung by a crooner on the television.
And that's pretty much it. The Art Deco male singer version can be heard for a few seconds in the CURRENT Carousel of Progress in the phonograph section.