They play a different music loop that's all over-the-top epic orchestral music. I can't tell if it's pieces from various movie soundtracks, or rip-off public domain songs that just sound suspiciously similar. At times, they've played it during the 10Ks through Epcot, but recently they seem to prefer pop versions of well known Disney songs for those
It may sound silly, but it's honestly one of my favorite parts of any race I've run, and I would also love to know the names of the tracks to add to my running mix. The whole thing is just so epic and glorious that you can't help but get swept up in it, especially with all the torches lit. Do you think it's a coincidence that my avatar is one of the World Showcase torches, as seen during the 5K?
After finishing this year we went back into the park to cheer for a friend, and watching people struggle to keep moving while this was playing was just so epic; I may or may not have been fighting back tears (though that could be part of the post-Marathon delusional haze that happens after any big race) since it really does a great job of making it feel like a monumental moment
Here's a short video from this year that has some of the loop (not sure how this person got into World Showcase while it was still dark, but I'm not complaining). From what I remember after the race this year, the entire loop is about 15-20 minutes
I'm not positive, but the music at the end of the video sounds like the Braveheart theme, though it would be a different (bagpipe-free) arrangement from what's in the film