When I was in college, I saw these guys
(I can't find many vids of them or a home page) play a show at my college...they were fantastic, my jaw was on the floor. for an encore, they said they were going to do something called "playing with hands," and one brother sat classical style, the other one stood behind him and they played an upbeat fingerstyle piece. It wasn't like one brother was just playing a bassline either, they were both going to town, and would switch which one was playing where on the neck and which strings, so it wasn't always the same. They had worked it out to be kind of funny too, they would stop at the same time for a split second and scratch each others chin or nose or stuff like that, it blew my mind. Wish I could find video of it.
anyway the guys are the Assad brothers from Brazil
and Vince, you have a PM