For his new mash-up show, Soundclash (airing tonight at 9pm on VH1), The Roots bandleader Ahmir “Questlove” Thompson pairs three artists from different genres and asks them to perform a concert together. Last week, he had rapper T.I. together with rockers Fall Out Boy and electro-pop outfit London Grammar. This week Sia, Ed Sheeran and Grouplove will perform. In honor of the show, we asked Questlove to tell us his three favorite most-unlikely duets of all time.