I don't really know, but I know you can apply digital effects to recorded audio, like distortion or delay/reverb (which are often used), it's possible he might have used distortion to fatten up his tone like an electric guitar, I've seen it being done on violins, I can see it being done in a studio with other instruments.
pretty much, doesnt sound exactly like that live, as in the "BOOM BOOM" bit he does is very powerful, and mustve been edited in production to have more of an umf, but its still pretty cool sounding live
All of that was done by Cello, including the ending (sounds get weird when you get all the way down the string). Only impossible part was where they had 3 things going on between two people.