The six groups in this episode include young chamber choir Tring Park 16, musical theatre enthusiasts from the West Midlands Crescendo, Oxford University a cappella group Oxford Alternotives, classical quintet Vox-Xover, all-female pop group Vocalities and all-male barbershop chorus The Ramparts. They must impress the panel of musical judges - Gareth Malone, Kelis and guest judge Joe Jonas.

The programme opens with an epic musical mash-up, and the groups then go head to head in a series of knockout choral challenges. First they each perform their show-stopper before battling it out with their opponent in a themed riff-off. The judges then decide which group goes through to the solo battles.

At the end of the programme only two groups remain, and they face the ultimate sing-off. They share the same song, before Joe Jonas joins in with the group the judges have chosen to go through. Show less