Created in 2005 by its director Caroline Redman Lusher, the Rock Choir has become something of a populist phenomenon. It’s a “people’s choir”, which means the songbook leans more towards Robbie Williams than Vaughan Williams. Anyone is welcome to join. There are no auditions and no talent requirements, a fact which will scarcely surprise viewers who last night witnessed the Bristol Rock Choir inflicting a very vocal form of GBH on ABBA's “Waterloo”.