Gareth Malone's exciting singing contest continues, as he searches for the nation's most entertaining amateur group who can perform a cappella - without instruments or backing tracks, they must rely solely on their voices. In this episode, Gareth mentors four new groups as they begin their battle to stay in his contest. Receiving Gareth's help and competing are a fledgling group of Salford students, a traditional male barbershop outfit from the Midlands, a gifted Glasgow University choir and an ambitious Birmingham six-piece, striving to bring a cappella to the masses. They will sing off in front of a live audience and a jury of world class a cappella experts. The jury's votes will decide which groups go through to the next stage and who will leave the contest for good.