Imagine you wanted to be play the full orchestral version of a movie theme, but you didn't have any musical instruments. I have a sneaking suspicion that Matthew Van Ness probably has some musical instruments, most likely quite a few, but he doesn't need them because he has his voice. And he uses his one voice to recreate the entire Indiana Jones theme, instrument by instrument, by himself. He's a one-manorchestra!
Oh, it's easy. Just take the full score, separate every instrumental part, sing each one at the precise tempo, and then mix them all together on a computer. Nothing to it. Of course, it helps if you can consistently carry a tune, which excludes me from even trying. Van Ness has been doing this for some time, and his YouTube channel might contain a particular favorite of yours.