In May 2015 Anne-Sophie Mutter put her noble, impressively named “Lord Dunn-Raven” Stradivarius through more than its usual paces. For a change, rather than standing on stage in one of the world’s renowned well-tempered grand concert halls, she spent two evenings playing in a tiny graffiti-scrawled nightclub in the Friedrichshain district of Berlin. The name of the club was Neue Heimat.