Largest choir - Guinness World Records

The largest choir consisted of 121,440 people and was organised by The Art of Living (India), in Perungalathur, Chennai, India, on 30 January 2011. The organisation for the event used 2,429 stewards and the choir sang in unison for over 5 minutes.

http://www.youtube.com/results?search_query=Naadha+Vaibhavam+Concert+Art+of+Living