Choirmaster Gareth Malone returns to create harmony in five of Britain's biggest workplaces. As the contest to be crowned 'best workplace choir' begins, he sets sail with P&O, the UK's longest-running cross-Channel ferry service. With choir members based at sea and on both sides of the English Channel, can Gareth create a musical entente cordiale?

Choirmaster Gareth Malone returns to create harmony in five of Britain's biggest workplaces. As the contest to be crowned 'best workplace choir' continues, Gareth travels to Birmingham to the biggest council in Europe. He discovers a singing traffic warden, a social worker soloist and a high-pitched gardener. With the next round of government cuts announced mid-rehearsals, some choir members may not have jobs at the end of the year.

Choirmaster Gareth Malone returns to create harmony in five of Britain's biggest workplaces. As the contest to be crowned 'best workplace choir' continues, Gareth checks out the talent at supermarket giant, Sainsbury's. When the choir's deepest bass breaks cover with his passion for Dolly Parton will the head office high flyers and the shop and depot workers finally sing with one voice, united by the Queen of country?

Choirmaster Gareth Malone feels the heat at Cheshire Fire and Rescue Service, as he continues his bid to find the year's best workplace choir. Bells and blue lights disrupt auditions but when rehearsals finally get underway Gareth tries to give the backroom staff the confidence to stand tall and be heard amidst the firefighters who attack choral singing with all sirens blaring.

As the contest to be crowned 'best workplace choir' continues, choirmaster Gareth Malone enters the embattled world of high finance, high flyers and rock bottom reputation at one of the biggest investment and trading banks in the world, Citi, in London's Canary Wharf. After imagining long lunches and cigars, Gareth finds himself in a lockdown during an anti-capitalist protest, learns how many noughts there are in a trillion, and creates his most musically accomplished workplace choir yet. When the bankers choose to sing Man in the Mirror, could it signal a moment of reflection, or will they drive on with technical ambition and ignore Gareth's attempts to find some heart?

In the quarter-final, all of the choirs finally come face to face when they arrive at Gareth's alma mater, the prestigious Royal Academy of Music, the place where he learnt his musical trade, along with the likes of Sir John Tavener, Sir Elton John and Lesley Garrett. The choirs undertake three days of intense tuition and tackle some of the giants of classical music which, after just 72 hours, they will perform to three world-class judges. Who will continue on their harmonious path with Gareth and show him that they know their Elgar from their elbow? Birmingham City Council struggles to make Vivaldi glorious, the Cheshire firefighters tackle operatic Verdi with all sirens blaring, and Sainsbury's says a prayer as they attempt Schubert's Ave Maria, while the Citi bankers are desperate to come up smelling of roses with their Flower Duet, and P&O Ferries delve into the depths of Mozart's Lacrimosa. After three of the most musically intense days of The Choir so far, which choirs will satisfy Gareth's determination that they achieve musical excellence?

Choirmaster Gareth Malone challenges the four remaining workplace choirs to find their souls, rhythm and conviction in a joyful bid to be crowned the year's best workplace choir. Three world class choral judges, an 800-strong audience and the London Community Gospel Choir await them at a celebration concert in one of the country's biggest gospel churches. Spirits are lifted at the fire service amidst news of strike action, the besuited bankers descend into dad dancing, the council workers try to rediscover belief in themselves and the ferry staff exuberantly rock the boat during rehearsals. On the night, potential soloists wait nervously for Gareth to decide who has the courage and fervour to step forward and improvise and lead their choir into the grand final.

The final of the competition takes place at Ely Cathedral, Cambridgeshire, where the three remaining choirs perform the world premier of a piece by composer Paul Mealor and lyricist Brendan Graham. Having been practising intensely for six months, the choirs are now challenged by choirmaster Gareth Malone to interpret the piece however they wish, meaning that within each choir, the members must agree on their strengths, their style and their stars. Performances, backed by the Ely Cathedral Choir, take place in a packed cathedral, where the most beautiful choral singing has resonated for a thousand years. It then falls to the three judges to decide who will be crowned best workplace choir.