At the "15th International A Capella Week Hannover" (German: "15. Internationale A-cappella-Woche Hannover") from April 4 to May 5, 2015, opened by Seveneleven in the "Neustädter Hof- und Stadtkirche" in Hannover, "Doris" and "Thomas Thomson" informed about it's roots, the Knabenchor Hannover...