You see, Smooth McGroove, known in the meatspace as Max Gleason, is someone who does acapella arrangements of tunes from video games. Not singing game songs that have had lyrics- this is a fair bit more interesting than that. He basically puts together remixes of game tracks using his own self as a sort of biological SoundFont for all of the individual parts of the game track he decided to arrange.
It's a bit hard to get in words, so some examples might help.
Collaboration with Dookieshed.
Oh, and he does take requests.