Pentatonix aren't a huge name on this side of the Atlantic, but in the US they're a pretty big deal.

The Texas-formed vocal harmony group won US reality show 'The Sing-Off' in 2011 and have since gone on to big deals and have sold a lot of records Stateside.

At last night's American Music Awards, they were accompanied by a 65-piece orchestra for their vocal Star Wars-themed medley.

Watch a clip of the epic performance, which came after a trailer for the new film was shown, below: