Global Festival curator Chris Martin also appears during Ed Sheeran's set to sing "Thinking Out Loud"
Singer-songwriters also take on Sean Kingston's 'Beautiful Girls' at Salt Lake City show
The London-based acoustic-folk artist recreates Aguilera's breakthrough hit "Dirrty"
Grammy nominees past and present break down six big categories
Star-packed celebration also features Stevie Wonder, Kylie Minogue, Tom Jones, more