According to Official Guinness Records,
The largest rap was achieved by 7,519 audience participants led by rapper Doppel-U (Christian Weirich) at a concert organised by Megarock Radio (Germany) in Erfurt, Thuringia, Germany, on 23 June 2010.
Clickers and log books were used for counting. Participants rapped the words to Schiller's "Ode to Joy."
For a complete list of 2010 records, please visit 2010 Guinness Records in Germany.