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?