For 'catters in the U.K., well, within striking distance of London.

If you're into harmony and acapell...accappel...acc...unaccompanied singing, there's a charity event for Water Aid in London on Sunday 15th. Sept. A lot of people will be singing stuff from Georgia (Eastern Europe) at Bernie Spain Gardens, a small park next to the Oxo Tower on the South Bank between Waterloo and Blackfriars Bridge starting at 14:30 You might want to come and have a listen (trust me, the harmonies are just wonderful).

nearest tube: Waterloo