“Aller Menschen werden Brüder” – “All men shall become brothers”. These are the words sung out by full chorus every time Beethoven’s Ninth Symphony reaches its ecstatic conclusion – and at a time of global conflict and domestic strife, it’s surely a sentiment that we can all embrace. At its Royal Albert Hall performance last night, the Proms audience did just that. This is a work now seen as a pinnacle of Western civilisation, but it has a singularly troubled and divisive history, which begins – as so often with musical matters – with politics. Was Beethoven a lefty? There’s...